Abstract Purpose To clarify the difference between the alpha angles measured by European method and by AIUM method. Materials and methods In this prospective study, infants less than 6-month-old with clinical suspicion of DDH were enrolled from the pediatric outpatient service in a large provincial teaching hospital from October 2022 to October 2023. The hips were examined according to the protocols described by AIUM guideline and by European consensus. The acetabular alpha angle was measured on the standard sections. Statistically significant difference between groups was determined by using a paired-sample t test. Results A total of 225 infants (median age, 4.0 months [interquartile range, 3.3–5.2 months]; 104 boys) were enrolled into the study. The mean value of alpha angle measured by AIUM method (62.1°; 95% CI 61.7, 62.4) was smaller than that by European method (63.4°; 95% CI 63.1, 63.7) (P