Background. Previously, we proposed interpolated averaged CT (IACT) for improved attenuation correction (AC) in thoracic PET/CT. This study aims to evaluate its feasibility and effectiveness on cardiac PET/CT. Methods. We simulated 18F-FDG distribution using the XCAT phantom with normal and abnormal cardiac uptake. Average activity and attenuation maps represented static PET and respiration average CT (ACT), respectively, while the attenuation maps of end-inspiration/ expiration represented 2 helical CTs (HCT). IACT was obtained by averaging the 2 extreme phases and the interpolated phases generated between them. Later, we recruited 4 patients who were scanned 1 hr post 315-428 MBq 18F-FDG injection. Simulated and clinical PET sinograms were reconstructed with AC using (1) HCT, (2) IACT, and (3) ACT. Polar plots and the 17-segment plots were analyzed. Two regions-of-interest were drawn on lesion and background area to obtain the intensity ratio (IR). Results. Polar plots of PETIACT-AC were more similar to PETACT-AC in both simulation and clinical data. Artifacts were observed in various segments in PETHCT-AC. IR differences of HCT as compared to the phantom were up to ~20%. Conclusions. IACT-AC reduced respiratory artifacts and improved PET/CT matching similarly to ACT-AC. It is a promising low-dose alternate of ACT for cardiac PET/CT.