Animals divergently selected for low and high residual feed intake (RFI) were fed either a high energy, low fiber (HELF) or low energy, high fiber (LEHF) diet. Regardless of line, pigs fed the LEHF diet had carcasses with reduced fat depth, loin depth, and greater percent lean. Line had no significant effect on carcass composition traits possibly due to line by sex interactions. Within the low RFI line, barrows had heavier carcasses with greater fat depth, while gilts had carcasses with a greater percent lean. Diet was the largest factor in final carcass composition of pigs in this study.