The project goal was to determine the effect of divergent selection for residual feed intake (RFI) on feeding either a high energy, low fiber (HELF) or a low energy, high fiber (LEHF) diet on carcass composition and quality traits. In experiment 1, 177 pigs of the ISU divergently selected RFI lines were randomly assigned to 8 mixed line and sex pens with 4 pens per diet. Slaughter occurred in 3 groups at a mean pig body weight of 121.5 kg. Data were analyzed using the mixed procedure of SAS with fixed effect of line, diet, sex, line*diet; random effects of slaughter group (SG), pen, litter and sire; off-test weight was as a covariate. Carcasses from LRFI animals has less fat depth, and greater loin depth and percent lean (<0.01), while carcasses from animals on the LEHF diet had a lesser HCW, fat depth, and greater percent lean (P<0.01). These data were also collected over generations (G) 8 and 9 on 315 pigs (G8=158, G9=157) on FIRE feeders; 6 pens of each diet per G. Pigs from G8 were harvested at a mean of 122.5 kg, and G9, 128.4 kg. Data were analyzed using the mixed procedure of SAS with fixed effect of line, diet, sex, G (except adipose), line*diet; random effects of SG, pen, litter, sire, and sensory day (sensory traits, cook loss, and star probe); off-test weight was fit as a covariate. Unlike experiment 1, loin depth tended to be greater carcasses from LRFI than HRFI pigs (P=0.09). Diet impacted composition the same as experiment1, except LEHF animals had a lesser loin depth (P<0.05) than HELF. LRFI animals on the HELF diet had the greatest loin depth (P<0.01) compared to other line by diet combinations. Loins from HRFI animals had greater drip loss, color scores, LM a* and b*, percent lipid, and lesser percent moisture (P<0.05). Chops from animals on the LEHF diet had lesser LM and adipose L* values and greater percent moisture than those from pigs fed the HELF diet. HRFI animals on the HELF diet had loins with the greatest percent lipid (P<0.05). Chops from LRFI pigs were juicer than those from HRFI (P<0.05), and gilts produced tougher loins than barrows (P<0.05). At 5 d postmortem (PM) loins from HRFI animals showed greater 38 kDa desmin degradation product (P=0.05), and d 2 PM loins from LRFI pigs on LEHF diet had the greatest degradation (P<0.05). Gilts (P=0.06) and LEHF (<0.01) fed pigs had adipose tissue with higher iodine value (IV) than barrows and HELF fed pigs, respectively. Improved efficiency has come at the cost of certain quality attributes, such as marbling and color. LEHF diet impacted all pigs in the same manner, resulting in poorer adipose tissue quality and lower IV.