Objectives Due to the increased losses of chloride and sodium in the sweat, CF infants are predisposed to develop episodes of hyponatremic/hypochloremic dehydration with hypokalemia and metabolic alkalosis, the condition sometimes referred to as pseudo-Bartter's syndrome in CF. The aims of study were to estimate the prevalence of this metabolic disorder among CF infants in our region and the influence of some clinical and genetic factors on its developing. Methods The records of all 90 newly diagnosed infants with CF in the period from 1998 to 2014 were reviewed. Laboratory, clinical and CFTR genotype data of patients with pseudo-Bartter's syndrome were analyzed. Results Nineteen infants had manifestations of electrolyte depletion with metabolic alkalosis, therefore the prevalence of pseudo-Bartter's syndrome among newly diagnosed infants with CF was 21%. Mean age of patients was 4.2 months (range 1–8). Most of them were breastfed. Mean values of blood pH, serum bicarbonate, sodium, chloride and potassium (mmol/L) were: 7.57±0.06, 43.71±7.23, 118.2±4.98, 67.7±8.23 and 2.7±0.46, respectively. Concerning CFTR genotypes of these patients, a great variability was found: F508del/F508del (8), F508del/G542X (3), F508del/621+G→T (1), F508del/457TAT→G (1), F508del/711+3A→G (1), G126D/V456F (1), G126D/E585X (1), F508del/Unknown (2) and Unknown/Unknown (1). Five of them were pancreatic sufficient. Conclusion This metabolic disorder is a common presenting manifestation of CF in infancy in our region. The possibility of CF should be seriously considered in any infant with metabolic alkalosis and hypoelectrolytemia, whether or not there are associated pulmonary and/or gastrointestinal symptoms.