The article deals with the factors influencing decisions and the consumer behavior in the market for consumer loans. It appoints the differences in the perception of credit costs in terms of economics and behavior. Its main objective is to determine how important are the nominal interest rate, total cost and the amount of monthly payment in the process of choosing a particular loan offer. Based on the conjoint analysis, conducted on a group of 105 adult Poles, who declared the contact with any form of credit, the author of the article proves the hypothesis that borrowers perceive the cost of borrowing under the assumptions of mental accounting. It also answers many research questions related to individual differences in the perception of credit costs and the relationship between declared attitudes toward borrowing and accounting of mental and materiality of the analyzed characteristics of the loan.