The objective of the study was to determine the impact of a probiotic Bifidobacterium lactis Bb-12 strain on the content of CLA in the fat of model ripening cheeses. The results suggest that under the encouraging ripening conditions, the Bifidobacterium lactis bacteria can favourably impact the CLA content in the fat of the model cheeses investigated. During ripening at a temperature of 14°C, a statistically important increase in the CLA content was found in the cheeses with a Bb-12 strain added, after the eighth week of ripening. This increase was about 60mg CLA/100g of fat. In the last week of ripening, the model cheeses met a requirement of the therapeutic minimum referring to probiotic products, and they contained ca. 10⁶ of live cells of Bifidobacterium bacteria per 1 gram of product.