The influence of synthesis conditions on thermodynamic properties of hydrides of LaNi2.5Co2.4Mn0.1 and LaNi2Co3 intermetallic compounds has been studied by means of the Tian-Calvet differential heat-conduction microcalorimetry. Two series of experiments were carried out at 308 and 353 K. The thermodynamic parameters in the LaNi2Co3 - H-2 system depend sufficiently on thermal prehistory of the intermetallic. It can be explained by possibility of different ways of transition metal ordering in their CaCu5-type lattice. The characteristics in LaNi2.5Co2.4Mn0.1 - H-2 system being invariable indicates only one way of transition metals ordering,