This paper addresses the efficiency of IDDQ and more specifically Delta-IDDQ testing when using a realistic short defect model that properly considers the relation between the resistance of the short and its detectability. The results clearly show that the Delta-IDDQ approach covers a large number of resistive shorts missed by conventional logic testing, requiring only a relatively small vector set. In ad- dition a significant number of defects which are proven to be undetectable by logic testing but may deteriorate and result in reliability failures are detected. The Delta-IDDQ threshold and thus the equipment sensitivity is shown to be critical for the test quality. Furthermore, the validity of the traditional IDDQ fault models when considering re- sistive short defects is found to be limited. For instance, the use of the fault-free next-state function for sequen- tial IDDQ fault simulation is shown to result in a wrong classification of some resistive short defects. This is the first systematic study of IDDQ testing of resistive short de- fects. The impact of the threshold on the defect cover- age is quantified for the first time. Although the simula- tion results are based upon a 0.35μm technology, the re- sults and methodology can be transferred to state-of-the- art and NanoTechnologies.