Peculiar features of Deep Level Transient Spectroscopy (DLTS) measurements on resistive samples are pointed out. Depending on the value of the sample resistance in series with the diode capacitance, the DLTS signal can be strongly reduced and even its sign may be reversed, entailing a possible confusion between majority and minority carrier traps. Means of detecting these effects are discussed and a correction procedure is proposed, based on varying the circuit impedance by means of an additional resistance in series with the sample. Illustrative examples include ion implanted silicon and the case of a germanium bicrystal.