Randomised controlled trials (RCTs) are considered to provide the most reliable evidence on the efficacy of interventions. The aim of this study was to describe the recruitment process of an RCT study set up to evaluate a Cognitive Behavioural Therapy (CBT) intervention programme for adolescent patients with dental anxiety (DA). The participants were recruited from a consecutive sample of adolescent patients (12-19 yrs old) referred for DA to a specialised pediatric dentistry clinic. Age, gender, and reason for referral were recorded for the possible eligible patients as part of the drop-out analysis of the recruitment process. Participants were then randomized to the intervention (CBT integrated with dental treatment) or control (adapted dental treatment) condition. In the recruitment process, 138 possible eligible patients met inclusion criteria, of these 55 were enrolled, 44 declined participation and 39 patients were excluded.The patients enrolled in the RCT did not differ from the non-participants with regard to age, gender or cause of referral. As a result of difficulties in the recruitment process, the study period was extended. The considerable proportion of non-participants as evident from the recruitment process may pose a threat to the external validity of the clinical trial. From a clinical perspective, the reasons for the lack of motivation to participate in behavioural interventions and the failure to appear warrant further investigation.