The performance of an average standard uptake value (SUV) over a 1-mL-volume sphere within an (18)F-FDG-positive lesion resulting in the highest possible value (SUVpeakW), was compared to that of an average SUV computed from the 40 hottest voxels, irrespective of their location within the lesion (SUVmax-40). METHODS A PET dynamic acquisition performed in 20 lung cancer lesions yielded for each SUV metric its mean value, relative measurement error and repeatability (MEr-R). RESULTS SUVpeakW mean value was significantly 9.66% lower than that of SUVmax-40 (P<0.0001). SUVpeakW and SUVmax-40 MEr-R were significantly lower than MEr-R of SUVmax (the hottest voxel): 9.35-13.21%, 8.84-12.49% versus 13.86-19.59% respectively (95%-CL; P<0.0001). Although being marginal, SUVpeakW MEr-R were not significantly greater than SUVmax-40 MEr-R (P = 0.086). CONCLUSION SUVmax-40 is more likely to represent the most metabolically active portions of tumors than SUVpeakW, with close variability performance.