AbstractTeam's cohesion is one of the most important factors of IT project execution effectiveness. Optimization of team's cohesion gives the possibility of reducing the risk of project failure. It also allows to increase the teamwork efficiency and thus optimize time of tasks execution, increase the guarantee of maintaining the scope of the project and the chance of achieving a given level of products quality. This article presents determination model of team's cohesion, in particular for teams working in Agile frameworks. Presented model is based on so called ‘role patterns’ and paradigm of fuzzy logic. It also presents optimization model of team members selection based on decision making in the so-called fuzzy environment.