Extensive studies were carried out on the involvement of the CCKergic system in anxiety-, panic- and stress-related behaviour. The stimulation of CCK-A or CCK-B receptors is implicated in the physical and psychological responses of CCK to stress. Furthermore, several selective CCK-B agonists produce anxiogenic-like effects, while CCK-B antagonists induce anxiolytic-like responses in several models of anxiety. However, BC264 a highly selective CCK-B agonist, does not produce anxiogenic-like effects but increases attention and/or memory. These effects are dependent on the dopaminergic systems. Together with biochemical data, this led to the hypothesis of the existence of two CCK-B binding sites, CCK-B1 and CCK-B2, which could correspond to different activation states of a single molecular entity. Investigations into CCK-B1 and CCK-B2 systems might be of critical interest, since only one site, CCK-B1, appears to be responsible for the effects of anxiety. Furthermore, the improvement of attention and/or memory processes by CCK, through CCK-B2 receptors, could offer a new perspective in the treatment of attention and/or memory disorders.