Cardiac involvement was evaluated by echocardiography in 26 young cystic fibrosis patients. The mean age was 48.4 months (range 3 months to 15 years). The findings were compared with 26 age- and sex-matched children without a history of cardiopulmonary complaints. All patients had normal values of left ventricular ejection fraction and fractional shortening. Interventricular septal and posterior left ventricular wall thicknesses were similar to control group but right ventricular free wall thickness was found greater than in the control group. Abnormal septal motion was documented in six patients. Right ventricular pre-ejection period to ventricular ejection time ratio was found over the upper limit of normal in two patients and there was a negative correlation with clinical Shwachman scores (r: -0.55). Left ventricular pre-ejection period to ventricular ejection time ratio was found over the upper limit of normal in five patients. For both mitral and tricuspid valves, the mean ratios of peak velocity during passive filling (E) phase of diastole to peak velocity during atrial contraction (A) phase were found significantly lower than in the control group (p < 0.05). Early diastolic peak velocity was similar to that in the control group but late atrial peak velocity was higher in the patient group (p < 0.05). Isovolumic relaxation time was found the same as in the control group. We conclude that cardiac changes in diastolic and systolic functions begin at very young ages in cystic fibrosis patients.