Abstract: Nowadays, the cooperation is considered as one of the basic paths of enterprise development. For many entities, it is a chance of improving or increasing competitiveness, for others it is a necessity because the lack of cooperation could cause serious perturbations. However, it is emphasized that the decision to cooperate must be conscious. The effect can be on one hand the benefits, on the other hand there is the possibility of generating losses. Due to the fact that most of the relations between the cooperating companies are antagonistic, it is worth considering the factors that guarantee the effectiveness of cooperation. This paper attempts to identify the key factors that favour and limit the effectiveness of inter-organizational collaboration. The first part of the paper presents theoretical reflections on the essence and nature of cooperation. The second one focuses on the result analysis of a survey on determinants of cooperation conducted during the year 2015 on a sample of 192 entities.