This study investigates whether the relationship between objective health parameters and general health perceptions was mediated by symptoms of dyspnoea and physical functioning in patients with chronic obstructive pulmonary disease (COPD) and patients with chronic heart failure (CHF). The different health parameters were organised according to Wilson and Cleary's conceptual model of patient outcomes (Wilson & Cleary (1995). Journal of the American Medical Association, 273, 59-65). Second, we investigated whether perceptions of personal control were related to the health parameters in the model. Consecutive patients with COPD and CHF were included from the outpatient clinics of a university hospital and a general hospital, and from a rehabilitation centre, all in the Netherlands. Ninety-five COPD patients (aged 65.0+/-9.3; forced expiratory volume in 1s (FEV1)<70%) were included and compared with 90 CHF patients (aged 59.6+/-10.0; left ventricular ejection fraction (LVEF)<45%). The relationship between objective health parameters (FEV1 or LVEF) and subjective health (self-reported physical functioning) was not mediated by symptoms of dyspnoea. FEV1 or LVEF and symptoms of dyspnoea were independently related to self-reported physical functioning, which was directly related to general health perceptions. Perceived health competence was related to symptoms of dyspnoea and general health perceptions in patients with either COPD or CHF. Although patients with COPD reported lower levels in all self-reported health parameters in the model than the patients with CHF, this study showed that the relations between the health parameters in the model were comparable for COPD and CHF patients.