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Purpose: To assess the significance of attenuation correction on sensitivity, specificity and diagnostic accuracy of myocardial perfusion SPECT. Methods: 102 patients referred for myocardial perfusion imaging (MPI) were divided into two groups: 42 patients (mean age: 54.6 ± 12.6) were enrolled in the group A, who had undergone coronary artery angiography, within six months of the scan. 60 patients (mean age: 49.79 ± 11.3) were placed in the group B who had a <15% pretest likelihood of CAD. Both non-corrected (NC) and attenuation corrected (AC) images were visually analyzed according to 17-segment model of the left ventricular cavity. Visual assessment derived sensitivity, specificity, diagnostic accuracy and normalcy rate of NC and AC sets of images were compared using McNemar test. Results: Sensitivity, specificity and diagnostic accuracy for detection of coronary artery disease were found to be 100%, 11% and 79% respectively for NC images and 66%, 78% and 68% for AC images. The p value was found to be significant in only the RCA territory. Normalcy rates in the group B population were 19% for NC image set and 74% for the AC image set. No significant difference on basis of BMI was observed in attenuation corrected scans. The technique appears to be more valuable in men. Conclusion: This study demonstrates that CT based attenuation corrected Tc-99mm sestamibi SPECT myocardial perfusion imaging significantly improved the specificity of the RCA territory compared with non-attenuation corrected Tc-99mm sestamibi SPECT myocardial perfusion imaging in both genders irrespective of BMI.