Adaptive cruise control (ACC), through the partial automation of the longitudinal driving task, is expected to increase driving comfort and assure a positive impact on road safety. Previous research showed that some side effects can result from the usage of the ACC. Those studies were mainly performed with drivers who never used the ACC before taking part in the experiments. For this reason, little information is available about how the ACC actually affects the driving task of real users of the system. In order to investigate the topic, two focus groups sessions were performed in Portugal with 13 ACC drivers. The findings revealed users’ satisfaction regarding the comfort and safety provided by the system. On the other hand, some cases of behavioural adaptations to the system were reported. Further research on the problem domain is suggested.