Controlled combustion synthesis (CS) was carried out in the TiH2-B system. Samples with different TiH2 levels (sample #1: 82wt%TiH2-18wt%B, sample #2:41wt%TiH2-41wt%Ti-18wt%B, sample #3:82wt%Ti-18wt%B) were studied to investigate the influence of the surface condition of the diluents (Ti in this study) on the level of exothermicity of the self-propagating reactions. Homogeneously mixed and then compressed pellets of samples #1-#3 (green compacts) were combustion synthesized in controlled fashion and in thermo explosion mode under vacuum. Thermal analysis under vacuum by DTA was carried out on the green compacts. XRD and SEM investigation were used for the examination of pressed and as-reacted pellets. It was observed that the exothermicity of the CS reactions can be increased when the amount of the activated, fresh surfaces of diluent Ti created by TiH2 decomposition during heating of the samples under vacuum is increased as in sample #1 [having the highest TiH2 content (82wt%) among the samples studied] thus promoting the better kinetics conditions (i.e., faster CS reactions) for chemical reactions.