Objective <p>This study aimed to evaluate the diagnostic performance of lung perfusion SPECT/CT using different interpretation criteria and compare it with computed tomography pulmonary angiography (CTPA) in patients with suspected pulmonary thromboembolism (PTE).</p> Methods <p>We retrospectively reviewed 38 patients who underwent both lung perfusion SPECT/CT and CTPA within one week. SPECT/CT images were interpreted using two criteria: a stringent criterion that considered only definite perfusion defects, and a broad criterion that included both definite defects and areas of decreased perfusion. CTPA images were assessed for the presence of filling defects in pulmonary arteries. Final diagnosis of PTE was determined by the treating physician based on clinical, laboratory, and imaging findings, including response to therapy.</p> Results <p>CTPA showed a sensitivity of 77.3%, specificity of 81.3%, and overall accuracy of 79.0%. Using the stringent criterion, SPECT/CT showed a sensitivity of 81.8%, specificity of 68.8%, and accuracy of 76.3%. The broad criterion increased sensitivity to 100.0% and negative predictive value, but specificity dropped to 31.3%, with overall accuracy of 71.1%. Among the two SPECT criteria, the stringent approach demonstrated a more balanced diagnostic performance.</p> Conclusions <p>The diagnostic performance of lung perfusion SPECT/CT varies depending on the interpretation criteria used. While the broad criterion maximizes sensitivity, the stringent criterion offers more balanced diagnostic accuracy and may serve as a practical alternative when CTPA is contraindicated.</p>