Respiration-correlated PET (RCPET) can reduce motion artifacts, but image quality generally decreases. The use of phase-by-phase attenuation correction (PAC) for RCPET using respiration-correlated CT (RCCT) requires large computational resources, and tumor positions will not always match correctly because of different binning methods for CT and PET. In this study, we investigated whether PAC for RCPET can be replaced by midventilation attenuation correction (MidV-AC) for a group of lung cancer patients. RCPET/CT scans of 19 non-small cell lung cancer patients were performed. List-mode PET and CT data were binned and reconstructed into 8 phases. Two AC methods for RCPET were applied. First, the corresponding 8 RCCT phases were used for PAC. Then MidV-AC was used. Analyses were performed in terms of standardized uptake values (SUVs), volume recovery, contrast, and signal-to-noise ratio (SNR). Average differences between PAC and MidV-AC for mean and maximum SUV were 1.0% and 0.9% (P = 0.007 and P = 0.002), respectively, whereas SNR, contrast, and volume did not differ significantly (P >or= 0.2). Large motion amplitudes and irregular breathing revealed larger differences between phase 1 and MidV-AC values. Differences in SUV, volume, SNR, and contrast between PAC as available in currently used clinical software and MidV-AC for RCPET are small. MidV-AC provides an excellent surrogate for PAC for most lung cancer patients encountered in clinical practice.