The main purpose of the article is to analyse the most important borrower characteristics determining preferences in the choice of the interest rate formula in mortgage contracts. Based on the PFSA statistics, the portfolio of newly-issued mortgages in 2016 was analysed to identify a group of consumers corresponding to the borrower characteristics who, in the light of European and global research, would be willing or obliged to choose a fixed interest rate. The conducted research shows that in Poland, the scale of the fixed interest rate choice in mortgage contracts is insignificant and represents only 0.2% of total mortgage debt. The analysis allows to identify a group of Polish consumers who should be given an option to choose a fixed rate when signing a mortgage contract. The size of the target group that should get acquainted with the offer of fixed-rate mortgages varies in Poland, depending on the chosen borrower characteristics. On the basis of the research, however, it can be incurred that in about 20% of the concluded contracts, there should be an option to choose the interest rate formula.