Objectives: To identify an empirical method for identifying patients with 'high expectations' of orthodontic treatment with fixed appliances using a questionnaire-based approach. Design: Secondary analysis of data from four studies which collected data on patients' expectations of orthodontic treatment using the same questionnaire. Setting: Secondary care orthodontic services. Participants: All four datasets comprised new patients aged 12-15 years, with no history of orthodontic treatment, who fulfilled the criteria for NHS treatment using the Index of Orthodontic Treatment Need (IOTN). Unpublished dataset 1 comprised 100 participants, while dataset 2 had 70 participants, dataset 3 had 67 participants and dataset 4 comprised 40 participants. Methods: The questionnaire utilised in all studies had a question which asked respondents to rate seven different expectations of outcome relating to straight teeth, better smile, ease of eating, speaking, cleaning teeth, improved career prospects and social confidence. Dataset 1 was analysed to determine the proportion of patients who had rated all seven outcome expectation items at a maximum score. Similar analyses were performed for the other three datasets to explore the trend in the proportion of patients with high expectations over time. Results: For dataset 1, 2.0% of participants had high expectations, as defined by their scores on the questionnaire. The proportions for the datasets 2, 3 and 4 were 4.0%, 4.5% and 2.5%, respectively. Conclusion: The method outlined provides an empirical basis for identifying patients with statistically infrequent high expectations. This can potentially help clinicians in the management of such patients.