Background Chronic obstructive pulmonary disease(COPD)and congestive heart failure(CHF)are two chronic diseases that affect negatively the functional condition and quality of life of patients.We assessed the effect of symptoms and clinical variables on the functional capacity and quality of life in COPD and CHF patients.Methods The study included 42 COPD and 39 CHF patients.In both patient groups,dyspnea was assessed using Borg scale;functional capacity by shuttle-walk and cardiopulmonary exercise test and quailty of life by short fOrm-36 (SF36).Results No statistically significant difference was found in neither of the two disease groups regarding the dyspnea score,shuttle-walk test and the maiority of subgroup scores of SF36 (P＞0.05).A statistically significant difference was obsewed in peak VO2 in favor of COPD group(P＜0.05).No significant relationship was established between dyspnea score and forced expiratory volume in one second(FEV1)in COPD patients,and left ventricular ejection fraction(L.VEF)in CHF patients (P＞0.05).A significant negative correlation was obsewed between dyspnea score and functional capacity tests in both disease groups(P＜0.05).On the other hand,no relationship was found between L-VEF and FEV1 and quailty of life and functional capacity (P＞0.05),Conclusions It was revealed that symptoms have an impact on functional capacity and quality of life in both disease groups,however,objective indicators of disease severity do not show a similar relationship.Therefore,in addition to the objective data related to the disease,we recommend that symptoms should also be taken into consideration to assess cardiopulmonary rehabilitation program and during following-up.