- Logic Colloquium 2023, Milan, June 5-9, 2023 (PC member),
- Tribute to Kurt Godel 2020, Brno, January 13-15, 2020 (PC member),
- Logic in Computer Science, New York City, USA, July 5-8, 2016 (PC member)
- Dagstuhl seminar Optimal algorithms and proofs, Schloss Dagstuhl, Germany, October 12.-17., 2014 (a co-organizer)
- Logic and Interactions, CIRM in Luminy, France, April 29 - May 3 2013 (PC member)
- Logic and Computational Complexity (within FLoC), Edinburgh, July 2010 (PC member).
- Theory and Applications of Models of Computing, Prague, June 2010, (Proof Complexity special session org.)
- Logic Colloquium, Bern, July 2008 (pc member, spec.sect. org.).
- New directions in proof complexity, a workshop at
the Isaac Newton Institute in Cambridge in April'06 (principal organizer).
- EMS Mathematical Weekend with section in Complexity of computations and proofs, September'04 (section organizer).
- 12th International congress on Logic, Methodology and Philosophy of Science, Ovideo, Spain, 2003 (chair of PC for math.logic).
- Circuit and Proof Complexity, International Centre for Mathematical Sciences, Edinburgh, October 2001 (principal organizer).
- Logic Colloquium, Vienna, August 2001 (program committee chair).
- 11th International Congress on Logic, Methodology, and Philosophy of Science, Jagiellonian University, Cracow, August 1999.
- Algebraic Methods and Arithmetic Circuits, DIMACS-DIMATIA Workshop, Rutgers University, New Brunswick, June, 1999.
- Proof Theory and Complexity, BRICS (Basic Research in Computer Science), University of Aarhus, August 1998.