The aim of this study was to evaluate the dietary fiber intake and the dietary habits of children with and without functional chronic constipation. We enrolled 58 children with functional chronic constipation and 58 controls without constipation matched for sex and age. Food and fiber intake were evaluated by 24 hour dietary recall and a complete clinical history was performed. The age of onset of constipation occurred during the first year of life in 55.4% of the patients while the median age of evaluation was 78 months. Soiling was found in 41.7% of patients. The median period of exclusive breast feeding was shorter (P = 0.002) in the constipation group (one month) than in the control group (three month). The proportion of constipation was similar for mothers of children of both groups as well as for siblings in both groups. The fathers of children with constipation presented higher frequency of constipation (12.3%) than the fathers of children in control group (1.8%), but the difference did not reach statistical significance (P = 0.06). The amount of food measured by 24 hour recall was similar in both groups. The calorie intake of constipated children (1526 +/- 585 calories/day) was lower (P = 0.07) than in the control group (1712 +/- 513 calories/day) but the difference did not reach statistical significance. The intake of protein, fat and iron was lower in the constipation group than in the control group. The volume of cow's milk intake was similar in both groups. The median of total dietary fiber intake in the constipation group (13.5 g/day) was statistically (P = 0.009) lower than in the control group (16.8 g/day). The daily intake of insoluble dietary fiber was also statistically lower (P = 0.001) in the constipation group (6.3 g) than in the control group (9.4 g). The intake of soluble dietary fiber was similar in both groups. The intake of dietary fiber per 1,000 calories of diet was 10.3 g in the constipation group and 10.4 in the control group (P = 0.41). There was a considerable intersection of individual values in fiber intake of the constipation and control groups, suggesting that low fiber intake acts in association with others factors on the genesis of constipation in children. However, the low intake of insoluble fiber, suggests that it plays an important role on the pathogenesis of chronic constipation in children.