Objective: To develop and validate a questionnaire to screen for potential nonadherence in patients with chronic ailments. Methods: Themes from qualitative interviews with chronic obstructive pulmonary disease patients were used in developing content of the questionnaire. The questionnaire was distributed to 525 ambulatory patients with chronic lung diseases. Principal components analysis was performed to identify the subscales in the questionnaire. Internal consistency, validity and stability of the subscales were also evaluated. Results: The 30-item Beliefs and Behaviour Questionnaire (BBQ) measures beliefs, experiences and adherent behaviour on five-point Likert-type scales. Two hundred and eighty patients (53.3 ) with a mean age of 71.1 years responded to the questionnaire. The beliefs section had a two-factor solution- confidence and concerns with internal consistencies of 0.82 and 0.45, respectively. The two domains identified from the section experiences -satisfaction and disappointment had internal consistencies of 0.85 and 0.52, respectively. The behaviour section, separately entitled the Tool for Adherence Behaviour Screening (TABS), had a two-factor solution- adherence and nonadherence , with internal consistencies of 0.80 and 0.59, respectively. All the domains demonstrated comparable reliabilities across two different patient populations. Their temporal stabilities ranged between 0.62 and 0.94. Conclusion: The validity, reliability and utility of the BBQ and the TABS, a sub-scale of the BBQ that screens both intentional and unintentional nonadherence to pharmacological and non-pharmacological disease management, have been established. Practice implications: The BBQ and the TABS have potential applications in screening adherence beliefs, experiences and behaviour in both clinical practice and research. (c) 2005 Elsevier Ireland Ltd. All rights reserved.