1 Abstract The submitted rigorous thesis comprehensively deals with the institute of participation in the offense in Czech criminal law (hereinafter referred as "complicity"). The thesis particularly focuses on de lege lata interpretation of the complicity, i.e. on existing legislation, Act. No. 40/2009 Coll., Criminal Code. The text contains numerous proposals de lege ferenda, which results from the critical approach to current regulation of the complicity in Czech legal system. The participation is a traditional and complicated topic of the criminal law doctrine. The issue of criminal liability for participation in the offense is one of the most complicated issues of criminal law theory and practice. The complexity of problem stems primar...