We have investigated the defect structure of ion-implanted and electron irradiated crystalline Si using deep level transient spectroscopy measurements to characterize both vacancy-(V) and interstitial- (I) type defects and to monitor their evolution upon annealing at temperatures ≤ 600 °C. It is found that only 4% of the Frenkel pairs generated by the energetic particles escape direct recombination and are stored into an equal number of room temperature stable V- and I-type defect complexes. No difference is found in the defect structure and annealing kinetics of ion implanted (1.2 MeV Si to fluences between 1×109 to 1010/cm2) and electron irradiated (9.2 MeV to fluences between 1 and 3×1015/cm2) samples in spite of the fact that denser collision cascades are produced by the ions. Annealing treatments result in a concomitant reduction in the concentration of I and V-type defects, demonstrating that defect recombination occurs preferentially in the bulk and not at the sample surface. Finally, at temperature above 300 °C, when most of the vacancy-type defects have been recombined, a residual concentration of I-type defects is found in ion implanted samples. This interstitial excess, not detected in electron irradiated samples, provides a direct evidence of the imbalance between I and V concentration produced by the extra incorporated ion.