Usability evaluation is an essential step in health care system development, including patient information websites. In this study we compared the think aloud method (TA) and the heuristic evaluation (HE) in a case study on the development of a website for childhood cancer survivors. Both methods managed to uncover all major problems with the website, though additionally HE found cosmetic issues and the TA found problems with website content. These findings contradict earlier studies but may be explained by the inclusion of two double experts in our study, presumably enabling them to take on the role of 'a patient' in testing the website. We nevertheless recommend the use of both methods if adequate funding and expertise are available; otherwise when HE usability evaluators are not familiar with the system domain, a work-domain expert could assist them in tackling domain-specific problems.