Chronic heart failure and airway obstruction produce overlapping syndromes. Existent criteria for the diagnosis and grading of airway obstruction based on spirometry results may be inadequate in the presence of coexistent cardiac failure. The cardiac component of pulmonary function tests (PFT) can be measured in patients undergoing orthotopic heart transplantation (OHT).Before and 1 year after OHT between 2006 and 2008 PFT were performed in 29 patients according to existent guideline. Willcoxon matched pair tests were used for analysis in Statistica 7.1. The general group characteristic included age, gender, New York Heart Association class, CCS class, body mass index, present medications, blood and chemistry tests, as well as exercise tolerance tests, right heart catheterization, and echocardiography results.One year after OHT we observed significant improvements in forced expiratory volume in the first second (FEV1) and its percent of normal value (FEV1%) as well as forced vital capacity (FVC), FVC%, vital capacity (VC) and VC%: namely, 2.56 L versus 2.96 L; 82% versus 93%; 3.30 L versus 3.81 L; 85% versus 97%; 3.38 L versus 4.04 L and 85% versus 100% (all P < .01). FEV1 and FVC increments of: 0.39 and 0.471 respectively, exceeded the cutoff point of 12% of predicted value established as the spirometry criterion for reversibility of obstruction. Elimination of heart failure by OHT did not significantly change the FEV1 to FVC ratio (FEV1%FVC).Chronic heart failure contributed to significant FEV1 reduction, which limits the usefulness of PFT for diagnosis and grading of airway obstruction. FEV1%FVC, the main diagnostic criterion of chronic obstructive lung disease, seems to be an index independent of concomittant heart function impairment.