The aim of the study was to investigate the effect of a hydrotherapy program on FVC, FEV, PEF, RR and SaO 2 on children with Down syndrome over six months and to compare it with a conventional respiratory physiotherapy program. Eighteen children, with Down Syndrome, aged 6-11 years (9.53 ± 0.454), divided into two groups of nine, the intervention group (IG), that participated in the hydrotherapy program and the control group (CG) participated in the classical physiotherapy program. We calculated mean values of FVC, FEV, PEF, RR and SaO 2 before and after six months intervention for both groups. There was a statistically significant improvement in all factors for both groups. However, were statistically more significant for the intervention group (IG). Based on a specific protocol of intervention in the water and at the same time with a group of children who participated in a similar program of classical respiratory physiotherapy, it was found to be statistically more important than the second group in improving respiratory function. We recommend the use of hydrotherapy as a complementary therapy that should be part of the weekly program of these children in addition to the existing treatments they attend.