Titanium thin films have been deposited on Si(100) wafers by electron beam evaporation in the 50-450 degrees C temperature range. Some samples were deposited in high vacuum conditions while others in a deuterium gas atmosphere with the aim to study the effect of the D-2 gas on the crystallographic orientation of the deposited layers. Compositional studies of the titanium films have been carried out by elastic recoil detection analysis and Rutherford backscattering spectroscopy, while structural analysis was performed by X-ray diffraction. It was found that Ti films deposited in a high vacuum present the (002) (minimum surface energy) preferred orientation. Titanium film deposited in a deuterium atmosphere at low temperatures present high concentration of adsorbed deuterium and show the (100) (maximum surface energy) preferred orientation; when deposited at high temperatures samples present very low deuterium concentrations and show again the (002) preferred orientation. A. possible explanation of the above results is that the surface mobility of Ti ad-atoms is limited by D-2 molecule adsorption, owing to the surface site occupancy.