Background. The aim of this study was to examine the quality of nitrogen 13-labeled ammonia (NH3) perfusion data from coincidence-capable gamma camera positron emission tomography (GC-PET) systems compared with that from full-ring positron emission tomography (FR-PET). Methods and Results. The performance parameters of the GC-PET system were examined and found adequate for imaging at the activity levels used clinically. We studied 15 patients who underwent stress and rest N-13-labeled NH3 perfusion imaging on FR-PET and GC-PET systems. Quantitative analysis of perfusion values showed that GC-PET uptake was significantly lower than FR-PET uptake in 67.6% of segments. Bland-Altman analysis showed that the mean difference between FR-PET and GC-PET values was from 5.3% to 5.9%. Stress FR-PET identified 49 segments as having impaired perfusion, 46 (93.9%) of which were also identified by GC-PET. Fifty-six additional segments were identified as abnormal by GC-PET. These findings indicated a general overestimation of defect size on GC-PET. Analysis of the degree of perfusion reduction also found that GC-PET tended to overestimate defect contrast. These findings are similar to those previously found by workers examining fluorine 18-fluorodeoxyglucose uptake by both techniques. Conclusions. Good concordance was shown between GC-PET and FR-PET systems for N-13-labeled NH3 perfusion imaging, although further work is required to optimize the technique.