Objective To evaluate the additional value of CACS in detection of coronary artery disease (CAD) with MPI. Methods A total of 188 suspected CAD patients (128 males, 60 females; average age (61.93±9.16) years) who underwent one-step examination of MPI combined with CACS from December 2012 to August 2014 were enrolled in this retrospective study. According to the gold standard of CAG, the diagnostic efficacy of MPI was calculated. ROC analysis was performed to determine the optimal CACS threshold for the detection of CAD. Mann-Whitney u test and χ2 test were used for statistical analysis. Results (1) Seventy-three CAD cases were confirmed (≥50% stenosis) among 188 patients. The sensitivity, specificity, accuracy for CAD diagnosis with MPI were 65.8%(48/73), 75.7%(87/115), 71.8%(135/188), respectively. Twenty-five CAD patients had negative findings with MPI, including 2 with LM disease, 4 with three-vessel disease (LAD+ LCX+ RCA, 3-VD), 3 with 2-VD, 16 cases with 1-VD. Among them 13 cases (52.0%, 13/25) had intermediate lesions of 1-VD (50%≤stenosis 0.05). (3) Of the 25 CAD patients with negative MPI results, 11(44.0%, 11/25) showed abnormal CACS(CACS≥95.1), consisted of 2 cases of LM disease, 4 cases of 3-VD, 2 cases of 2-VD, 3 cases of 1-VD. Diagnosis was corrected by CACS in 8/9 cases of severe CAD (LM CAD or multivessel disease) which were missed by MPI. Conclusion CACS could offer additional information for MPI in detection of suspected CAD patients, which can improve the sensitivity of MPI for diagnosing CAD, especially for severe CAD with LM lesions or multivessel CAD. Key words: Coronary disease; Myocardial perfusion imaging; Tomography, emission-computed, single-photon; Technetium Tc 99m sestamibi