Purpose: To evaluate the efficacy of synbiotic formula with partial whey hydrolysate and high magnesium content in infants presenting with functional constipation.Methods: Sixty-five infants with functional constipation were included. Forty infants were treated during one month with parental reassurance and the intervention formula and were compared to a control group of 25 infants treated with parental reassurance only. Parents completed a quality of life (QoL) questionnaire at baseline and during the last week of the study.Results: At inclusion, stool characteristics and QoL were similar in both groups. The control group was slightly older than the intervention group (7.5±3.9 vs. 6.2±3.6 weeks). At onset, stool composition was "hard and tight" (Bristol stool scale 1 and 2) in all infants. After one month, stool composition remained unchanged in the control group except in two infants that developed "creamy" stools (Bristol stool scale type 3 and 4). In the intervention group, stools remained "hard and tight" in 27.5%, and became "creamy" in 47.5%, "loose" (Bristol stool scale type 5) in 22.5% and "watery" (Bristol stool type 6 and 7) in 2.5%. The benefit of the intervention formula was estimated to be "very important" in 70%. The median scores for QoL improved significantly in the intervention group for all parameters and for one in the control group.Conclusion: The intervention formula significantly improved functional constipation resulting in a better QoL of the parents and infants.