1. 2023. Conference co-chair του joint EGOV 2022 (22st International Conference on eGovernment – CEDEM – 15th International Conference on eParticipation (ePart)), 4-7/9/2022, Budapest, Sweden.
2. 2022. Conference co-chair του joint EGOV 2022 (21st International Conference on eGovernment – CEDEM – 14th International Conference on eParticipation (ePart)), 6-8/9/2022, Linköping, Sweden.
3. 2021. Conference co-chair του joint EGOV 2021 (20th International Conference on eGovernment – CEDEM – 13th International Conference on eParticipation (ePart)), 7-9/9/2021, online / Granada, Spain.
4. 2020. Conference co-chair του joint EGOV 2020 (19th International Conference on eGovernment – CEDEM – 12th International Conference on eParticipation (ePart)), 31/8-2/9/2020, online λόγω κορονοϊού.
5. 2019. Conference co-chair του joint EGOV 2019 (18th International Conference on eGovernment – CEDEM – 11th International Conference on eParticipation (ePart)), 2-4/9/2019, San Benedetto Del Tronto, Italy.
6. 2018. Conference co-chair του joint EGOV conference (17th International Conference on eGovernment (EGOV) – CEDEM – 10th International Conference on eParticipation (ePart)), 3-5/9/2018, Krems, Austria.
7. 2017 Conference co-chair του 9th International Conference on eParticipation (ePart) και co-chair of the 16th International Conference on eGovernment (EGOV), 4-7/9/2017, St. Petersburg, Russia.
8. 2016 Conference lead chair του 8th International Conference on eParticipation (ePart) και co-chair of the 15th International Conference on eGovernment (EGOV), 5-8/9/2016, Guimarães, Portugal.
9. 2015 Conference lead chair του 7th International Conference on eParticipation (ePart) και lead chair of the 14th International Conference on eGovernment (EGOV), 30/8-2/9/2015, Thessaloniki, Greece.
10. 2014 Conference lead chair του 6th International Conference on eParticipation (ePart) και co-chair of the 13th International Conference on eGovernment (EGOV), 2-3/9/2014, Dublin, Ireland.
11. 2013 Conference co-chair του 5th International Conference on eParticipation (ePart) και co-chair of the 12th International Conference on eGovernment (EGOV), 17-19/9/2013, Koblenz, Germany.
12. 2012 Conference lead chair του 4th International Conference on eParticipation (ePart) και co-chair of the 11th International Conference on eGovernment (EGOV), 3-5/9/2012, Kristiansand, Norway.
13. 2011 Conference lead chair του 3rd International Conference on eParticipation (ePart) και co-chair of the 10th International Conference on eGovernment (EGOV), 29/8-1/9/2011, Delft, The Netherlands.
14. 2010 Conference lead chair του 2nd International Conference on eParticipation (ePart) και co-chair of the 9th International Conference on eGovernment (EGOV), 29/8-2/9/2010, Lausanne, Switzerland.
15. 2009. Conference lead co-chair του 1st International Conference on eParticipation (ePart) και co-chair of the 8th International Conference on eGovernment (EGOV), 31/8-4/9/2009, Linz, Austria.

1. 2020. Track Co-chair του Track “Governance of Technologies and Data in Social Innovations” (Track chairs: Loni Hagen, Iryna Susha, Efthimios Tambouris) στα πλαίσια του 21st Annual International Conference on Digital Government Research conference (dg.o 2020).
2. 2019. Track Co-chair του Track “From Data Intelligence to Data Impacts: Tackling Public Problems with Data” (Track chairs: Iryna Susha, Efthimios Tambouris, and Yushim Kim), στα πλαίσια του 20th Annual International Conference on Digital Government Research conference (dg.o 2019).
3. 2018. Track Co-chair του Track “Data Sharing and Analytics to Address Societal Challenges” (Track chairs: Efthimios Tambouris, Iryna Susha, and Yushim Kim), στα πλαίσια του 19th Annual International Conference on Digital Government Research conference (dg.o 2018).

1. 2016. Φιλοξενούμενος εκδότης (με τους P. Panagiotopoulos, O. Saebo και Κ.Ταραμπάνη) του Ειδικού Τεύχους “eParticipation” για το International Journal of Electronic Governance (IJEG).
2. 2011. Φιλοξενούμενος εκδότης (με τον Ass. Prof. O. Glassey και την Prof. Th. Pardo) του Ειδικού Τεύχους “Open Government and Open Information” για το eJournal of eDemocracy and Open Government (JeDEM).
3. 2008. Φιλοξενούμενος εκδότης (με τον καθηγητή Κ. Ταραμπάνη) του Ειδικού Τεύχους “One-Stop Government” για το International Journal of Electronic Governance (IJEG).

1. 2019-τώρα. Associate editor του Digital Government (DGOV), νέου περιοδικού της ACM στον τομέα της Ηλ/κής Διακυβέρνησης
2. 2017-2021 (2 θητείες). Associate editor του Government Information Quarterly (GIQ), καλύτερου περιοδικού στον τομέα της Ηλ/κής Διακυβέρνησης (2016 IF = 4) (Από το 2015-τώρα: Μέλος του editorial board)
3. 2017. Αξιολογητής για το Information Systems Frontiers
4. 2015, 2011. Αξιολογητής για το International Journal of Electronic Governance (IJEG)
5. 2014. Αξιολογητής για το New Media and Society
6. 2014. Αξιολογητής για το Computer (Special Issue 2014: e-Government Interoperability)
7. 2014, 2009. Αξιολογητής για το Information Polity (Special Issue 2014: Smart Government, Citizen Participation, and Open Data; Special Issue 2009: Social Networks: Making Connections between Citizens, Data & Government)
8. 2013, 2012. Αξιολογητής για το Government Information Quarterly (GIQ)
9. 2013. Αξιολογητής για το International Journal of Social Media and Interactive Learning Environments (IJSMILE)
10. 2012. Αξιολογητής για το International Journal of Public Sector Management
11. 2012. Αξιολογητής για το Future Internet
12. 2011, 2009. Αξιολογητής για το IEEE Intelligent Systems (Special Issue 2011: Linked Open Government Data; Special Issue 2009: Transforming E-government & E-participation)
13. 2009-2010. Αξιολογητής για το European Journal of Information Systems(Special Issue: Information Systems Research, Education and Policy in the Mediterranean Region)
14. 2009. Αξιολογητής για τοThe Information Society Journal
15. 2009. Αξιολογητής για το Communications of the Association for Information Systems
16. 2008. Αξιολογητής για το International Journal of E-Democracy(IJED) (Special Issue: E-Government for Small and Medium sized Enterprises (SMEs) in Rural Areas)
17. 2005. Αξιολογητής για το International Journal of E-government

Σταθερός Committee Member και Reviewer για τα συνέδρια:

1. 2001-τώρα: International Conference in Electronic Government (EGOV)
2. 2006-τώρα: HICSS Conference
3. 2007-τώρα: International Conference of Digital Government Research (dg.o)
4. 2012-τώρα: International Conference on Theory and Practice of Electronic Governance (ICEGOV)
5. 2012-τώρα: IADIS International Conference Information Systems
6. 2015-τώρα: Balkan Conference in Informatics (BCI)

Περιστασιακός (ad hoc) Committee Member and Reviewer σε πολλά συνέδρια, tracks και workshops, όπως:

1. 17th European Mediterranean & Middle Eastern Conference on Information Systems (EMCIS 2020) – Track PC Member (Digital Government);
2. International Conference on Deliberation and Decision Making Interdisciplinary Perspectives on Civic Tech (2018);
3. 25th European Conference on Information Systems (ECIS) (2017);
4. International Conference on Enterprise Information Systems (ICEIS) (2017);
5. International Conference on Business Informatics (CBI) (2017);
6. International Conference for E-Democracy and Open Government (CEDEM) (2014);
7. European Conference on Modelling and Simulation (ECMS) (2013);
8. European Conference on Information Systems (ECIS) [Role: Associate Editor] (2012);
9. European Semantic Web Conference (ESWC 2012) (2012);
10. E-Government and E-Services Conference (EGES) within the World Computer Congress (WCC) (2010);
11. 1st International ICST Conference on e-Infrastructure and e-Services for Developing Countries (AFRICOMM 2009);
12. 2nd International Conference on Data Engineering and Management (2010);
13. 2nd International Conference on Networked Digital Technologies (NDT2010);
14. 3rd International Conference on Digital Information Management (ICDIM 2008);
15. Workshops organized by TerreGov project at the field of eGovernment Interoperability;
16. European mGovernment Conference (2006);
17. International Workshop “Dependability and Security in e-Government”. DeSeGov 2006, within the First International Conference on Availability, Reliability and Security (ARES 2006);
18. eGovernment Track within the 13th European Conference on Information Systems (ECIS) (2005);
19. TED Conference on eGovernment, (2005);
20. Annual Working Conference Knowledge Management in Government (2004);
21. Annual Bled E-commerce conference (2003).

1. 2016. Μέλος ομάδας της πρότασης «Ανοικτή Ελληνική Νομοθεσία» που διακρίθηκε στις 10 καλύτερες συμμετοχές στον 1ο Διαγωνισμό Καινοτομίας “IT 4 gov” του Υπουργείου Εσωτερικών και Διοικητικής Ανασυγκρότησης που διενεργήθηκε σε συνεργασία με το Υπουργείο Παιδείας, Έρευνας και Θρησκευμάτων και το Υπουργείο Οικονομίας, Ανάπτυξης και Τουρισμού.