The influence of feed energy concentration on the effect of betaine and chromium picolinate added to feeds, either separately or together, on fattening performance, carcass quality and some blood biochemical indicators was investigated in an experiment involving 128 pigs fattened from about 30 to 113 kg body weight assigned to 4 groups. The animals given feed with an increased energy content achieved 38 g better daily weight gains in the first period of fattening, and at the end of fattening their carcasses were similar to those of animals that received the diet with a lower energy concentration. The results of the experiment showed that the supplements improved fattening performance, especially in animals given chromium picolinate (902 g vs 857 g of body weight gain in the experimental and control groups, respectively). This effect was especially distinct in pigs fed diets with higher energy concentrations. They also improved their leanness from 56.0 to 57.5% and slightly decreased their backfat thickness. The combined supplement of betaine and chromium picolinate proved inefficient both for fattening and slaughter traits, although it decreased blood cholesterol, especially its LDL fraction by 9%. Gilts had lower weight gains than barrows and better results of post-slaughter evaluation regardless of the supplement used.