In this paper, we investigate the conformational behaviour of new pseudopeptide CCK 2 agonists based on the common template R-Trp-NMeNle-Asp-PheNH 2 where only the N-terminal substituent R varies. These compounds could be separated into two families according to their pharmacological profile: CCK 2A or CCK 2B . The conformational space of each compound was explored using molecular dynamics simulations and their structural properties were investigated. Our results suggest the occurrence of two families of conformations, extended and folded. Furthermore, this study brings out a possible correspondence between the CCK 2 pharmacological profile and the conformational behaviour of the compounds analysed. A model of preferential conformation is proposed for each compound. This work may provide a key to understand the mechanisms underlying the heterogeneity of CCK 2 receptor-associated pharmacological effects.