The purpose of this work is to estimate the quality of diagnostics of acute flaccid paresis (AFP) for the period of 2004-2007 and to define the importance of vaccinal strains of poliomyelitis virus in their origin. There were 81 patients under observation who were taken the childrens department in hospital № 40 in Ekaterinburg. 351 children were sent for diagnostics of AFP. The diagnosis of AFP at 165 children (47 %) was denied and after conducting additional examination the diagnosis of AFP has also denied at 97 patients (27,6 %). The diagnosis AFP 89 patients (25,4 %) was confirmed. Various vaccinal strains of poliomyelitis virus were detected at 8 % of patients. In most cases it is correct to consider mild spinal forms of vaccinal poliomyelitis the origin of which is caused by high variability of vaccinal strains of polio viruses which makes the liquidation of poliomyelitis nowadays impossible.