Crouzon syndrome is a cranio-facial dysostosis with autosomal dominant transmission and a birth prevalence of 16.5 per million newborns. Up till now there is no publications in polish medical journals about ultrasonic diagnosis of Crouzon syndrome or of any other craniostenosis. The development of ultrasonography, three-dimensional ultrasonography and in the last years also MRI, allows earlier detection and diagnosis of fetal malformation and enables precise evaluation of his anatomy. The aim of the study is presentatoin Crouzon syndrom diagnosed prenatally by ultrasonography and confirmed moleculary by DNA analysis. We would like to stress the diagnostic problems and the difficult decisions that we encountered.