OBJECTIVE To determine the sensitivity and specificity of thallium scintigraphy in detection of coronary artery disease in diabetic patients. METHODS Cross-sectional validation study. METHODS The study was carried out from July to December 2007 in the Cardiology Department of the Pakistan Institute of Medical Sciences, Islamabad. METHODS A total of 60 diabetic patients suspected of having coronary artery disease were studied. Systematic probability sampling technique was used during their selection. All the patients underwent thallium scintigraphy followed by coronary angiography, which was used as gold standard test. RESULTS Out of 60 patients, 44 had positive thallium scintigraphy and 16 were negative. Likewise, 46 had positive angiography and 14 were negative. Out of 46 patients with positive angiography, thallium scintigraphy was positive in 41 subjects (sensitivity 89%) and false negative in only 5 of the 46 patients. Out of 14 patients with negative angiography, 11 patients had a negative thallium scintigraphy (specificity 79%) and the remaining 3 had a positive thallium scintigraphy. This gives thallium scintigraphy a positive predictive value of 93% and a negative predictive value of 69% when compared with angiography. CONCLUSIONS Thallium scintigraphy is a useful modality in the detection of coronary artery disease in diabetic patients.