The article discusses the types of dangerous defects in welded joints. The main methods of non-destructive testing are described, their advantages and disadvantages are briefly reflected. The comparison of the automated ultrasonic testing methods with radiographic ones is given on the example of testing the welded joints of ASME DN350 Py250 pipe fittings with a thickness of the welded edges of 53.9 ÷ 61.3 mm. The comparison results of the methods by the criterion of the accuracy of determining the coordinates of defects are presented, which show the expediency of replacing the automated ultrasonic method with the radiographic one, provided that the thickness of the welded edges is shallow.