Crystals of 11 hydrated complexes consisting of alpha-amino acids, dipeptides, tripeptides and 18-crown-6 were isolated. The composition and thermal behaviour of these compounds were investigated and the temperatures, heat effects and activation energies of different stages of their decomposition were determined using DSC and TG. After preliminary dehydration at 300-350 K, the compounds undergo decomposition in one or two stages. It was found that the thermokinetic characteristics of the complexes are very sensitive to their structural features.