Pseudo-Bartter Syndrome (PBS), although quite common in patients with cystic fibrosis (CF), is often missed as simple dehydration or Bartter syndrome. This study was performed in patients with PBS to compare the pattern and course of the disease with those with CF not manifesting with this syndrome. All patients with CF who attended the respiratory clinic at Queen Rania Al-Abdallah Hospital from January 2000 to April 2010 were included in this retrospective case-control study. A specially formulated data sheet was used and those with PBS and those not having the syndrome were identified. A total of 110 patients (51% female) with CF with a median age of seven years were followed-up. Eighteen (16.3%) of them had one or more episodes of PBS. The median follow-up period was 6.2 years. All the episodes occurred during summer and in infancy. Median age of the initial episode of PBS was three months. One-third of them were initially followed at the nephrology clinic. Three patterns of PBS were identified: single episode in three (16.6%) patients, recurrent in 12 (66.6%) patients and chronic in three (16.6%) patients. Early colonization of Pseudomonas spp before 1 st birthday was seen in 44% patients with PBS compared with 12% in other CF patients (P-value = 0.0075). The total number of colonized patients and other CF features at the time of the study did not differ significantly among patients, although the mean Shwachman-Kulczycki score is significantly lower in those with recurrent PBS (69 compared with 85 in other CF patients). Gene mutation was identified in only 30% of the entire cohort. PBS is common in patients with CF, and it should be kept in mind in any patient with hypotonic dehydration and metabolic alkalosis. Recurrent pattern is associated with earlier Pseudomonas colonization.