Previous studies have suggested that ST-segment depression with adenosine myocardial perfusion imaging (MPI) may be a marker of significant coronary artery disease (CAD). It is unclear if the significance of ST depression differs between men and women. We investigated the diagnostic accuracy of ST-segment depression with adenosine radionuclide MPI as a marker of significant CAD in men and women. Consecutive patients who had angina or suspected CAD and underwent an adenosine stress test and subsequent angiography were retrospectively analyzed. The inclusion criteria were met by 959 patients. Mean age was 64 ± 11 years, and 43% were women. ST depression occurred in 7.6% of the cohort and more often in women (64% women vs 36% men, p <0.001). Among men and women, patients with ST-segment depression had a significantly higher peak rate–pressure product, more chest pain, and a higher ejection fraction in response to the adenosine infusion compared with those without ST-segment depression. ST-segment depression occurred more often in the presence of stenotic lesions (≥50% and ≥70%), and left main or 3-vessel disease, regardless of gender. Transient ischemic dilation occurred more often in men with ST-segment depression. The logistic regression analysis demonstrated that the only significant predictors of left main or 3-vessel CAD were gender, an abnormal result on MPI, transient ischemic dilation, and ST-segment depression. In conclusion, ST-segment depression during adenosine MPI is an important marker of angiographically significant CAD in men and women. The presence of ST-segment depression is associated with left main disease and 3-vessel CAD.