The cost attribute is of particular importance in discrete choice experiments since estimates of the cost coefficients are often used to calculate the marginal willingness to pay for the other attributes included. Only few studies have investigated how the inclusion of a cost attribute in discrete choice experiments affects preferences, and this study is the first to explore the effect of a cost attribute on both forced and unforced choices. In the empirical contribution, patients’ preferences for the organisation of general practice in Denmark are elicited. The cost attribute is operationalised as user fees for the consultation. Other attributes included are: waiting time in the telephone, opening hours, waiting time to the appointment, distance to the general practice, waiting time in the waiting room, consultation time, and whether the general practitioner or assisting personnel performs routine tasks. A representative sample of 1435 respondents from the Danish population with respect to age, gender, and geography answered the discrete choice experiment in a web-based questionnaire with a random split including/excluding the cost attribute. The two groups were asked to make both forced and unforced choices in each choice set. Our results show that in the unforced choice utility and scale parameters were not affected and the rank order remained the same when a cost attribute was included. In the forced choice the test of equal utility parameters was rejected, and rank order, marginal rates of substitution, and variance was shown to differ between the two groups. We observed that the inclusion of a cost attribute tended to change underlying choice behaviour. Evidence of dominant preferences was found in all splits. Overall, our results provide important knowledge on the effect of including a cost attribute in forced as well as unforced choices.