Combined unreactive mechanical alloying and controlled combustion synthesis (CS) was carried out in the TiH2-B system Samples with different compositions (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 particle size of reactants on the degree of conversion of the self-propagating reactions together with the other effects of mechanical alloying (MA) on CS technique. In the first step mixtures of samples #1 to #3 were converted into fine, crystalline forms without compound formation. For this purpose, unreactive mechanical alloying for up to 8 hours of time under Ar with forced air cooling to keep the temperature at room temperature were utilised. Mechanically alloyed powder samples were then examined by XRD and SEM study. Mixed, unreactively mechanically alloyed and then cold compressed pellets of samples #1-#3 (green compacts) were subsequently combustion synthesized in controlled fashion mode under vacuum to develop Ti-boride compounds formation (TiB and TiB, depending on the composition). Thermal analysis under vacuum by Differential Thermal Analysis (DTA) was carried out on the green compacts. XRD and SEM investigation were used for the examination of unreactively mechanically alloyed, cold-pressed, and as-reacted pellets via CS. It was observed that the degree of conversion 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 by using finer TiH2 particles obtained by mechanical alloying leading to the creation of more activated Ti surface in sample #1 compared to sample #3 thus promoting the better kinetics conditions (i. e., faster CS reactions) for chemical reactions, especially in sample #1 for it has the highest TiH2 content (82wt%) among the samples studied.