© 2014, Medical Association of Thailand. All rights reserved. Objective: To determine the degree of adherence to guidelines on the diagnosis of cephalopelvic disproportion (CPD) in Maharaj Nakorn Chiang Mai Hospital. Material and Method: The database of pregnant women who underwent cesarean delivery due to CPD between 2010 and 2012 was reviewed. The degree of adherence to guidelines on the CPD diagnosis was recorded. The guidelines were from Royal Thai College of Obstetricians and Gynecologists (RTCOG) and the American Congress of Obstetricians and Gynecologists (ACOG) as gold standard criteria for CPD diagnosis. Results: Four hundred sixty four pregnant women diagnosed as CPD were recruited. The adherence to guidelines either RTCOG or ACOG criteria was 80.4%. Of 91 cases that had incomplete criteria to diagnose CPD, 25 cases (27.5%) had been suspected of fetal macrosomia and CPD was diagnosed during latent phase of labor. Unfortunately, 76% of these fetuses had birth weight less than 4000 grams, which were unlikely to be macrosomia. Conclusion: The adherence to guidelines on the diagnosis of CPD was 80.4%. Almost one-third of the cases that had no adherence were false diagnosed of fetal macrosomia. Therefore, the strategy of accurate fetal weigh estimation may reduce unnecessary cesarean section from false diagnosis of CPD.