Background. Several different orthoses are used for the treatment of developmental dysplasia of the hip (DDH). The most popular are the Frejka pillow, the Pavlik harness, the von Rosen splint, and the Koszla splint. The purpose of our study was a retrospective comparative analysis of the non-surgical treatment of DDH using Pavlik harness and Frejka pillow. Material and methods. We studied 238 children (438 hips), 213 girls and 25 boys. In this group 143 children were treated using the Frejka pillow and 95 using the Pavlik harness. The development of the infants' hips was assessed by ultrasonography. Results. 89% of the hips treated with Frejka pillow and 95% treated with Pavlik harness were successfully reduced. In children with dysplastic hips diagnosed before age 24 weeks, the Pavlik harness is effective. In childrern diagnosed after 24 weeks of life the Frejka pillow is more effective. In spite of appropriate treatment using both methods, avascular necrosis was found in 12% of the hips treated with Frejka pillow and 7% in the Pavlik group. Conclusions. Pavlik-stabilized hips in human position to promote concentric reduction shorten the duration of treatment, allow the mother to clean the infant easily and decrease the risk of avascular necrosis. The position achieved by using the Frejka pillow is not as appropriate, but the results are better than with the Pavlik harness in children diagnosed after 6 months of age.