Dyspnea-related anxiety may lead to reduced quality of life and functional disability through fearful avoidance of dyspnea-evoking activity. We describe the validation of a generic - diagnosis-independent - instrument assessing dyspnea-related anxiety. A total of 187 patients with respiratory diseases completed the Breathlessness Beliefs Questionnaire (BBQ), a 17-item questionnaire adapted from the Tampa Scale for Kinesiophobia (TSK), a measure of how harmful pain patients think painful movement is and to what extent they think activity should be avoided. Measures of negative and positive affectivity (PANAS), anxiety and depression (HADS), functional status (PFSDQ), and health-related quality of life (CRDQ) were also completed. Principal component analysis and item-total correlations suggested a reliable (reduced) 11-item BBQ (Cronbach's alpha = .85) with two factors converging with the TSK factors: a 'somatic focus' factor assessing the harmfulness of dyspnea and the underlying pathology and an 'activity avoidance' factor assessing beliefs that activity should be avoided. Correlational analyses support the construct validity of the BBQ: higher scores on the BBQ are associated with reduced health-related quality of life and functional status. Associations between 'somatic focus' and negative affectivity and anxiety and between 'activity avoidance' and positive affectivity and depression further supported the validity of the BBQ and its subscales. The BBQ is a valid, short, and useful instrument to assess respiratory patients' beliefs about the harmfulness of their disease and physical activities. Further research is needed to document to what extent BBQ scores are related to daily life activities and symptoms.