Abstract Background: Pancreatic Ductal Adenocarcinoma (PDAC) is one of the deadliest cancers presenting an increased mortality rate of about 3% of all cancers and about 7% of all cancer death in the United States and Europe. One of them, used for long as potential independent predictor of surgery is the Sialylated Lewis blood group carbohydrate antigen 19.9 (CA19.9). CA19.9 is detected in low levels in healthy indi-viduals (up to 37U/ml) and the level is elevated in several types of cancers including pancreatic, and also in benign conditions such as pancreatitis and choledocholithiasis. Aim of Study: To evaluate the diagnostic value of CA19.9 in predicting the resectability of pancreatic cancer. Patients and Methods: This is prospective and retrospec-tive study which was carried out on 25 patients diagnosed as patients with biopsy-proved adenocarcinoma of the pancreas. All patients were selected from Eldemerdash Hospital Uni-versity, Ain-Shams University Hospitals in the period from January 2016 to April 2019. Results: The majority of the patients have cancer head of pancreas (72%), while 20% were confined to the body and 8% were confined to the body and tail. The majority of patients (44%) underwent pancreaticoduodenectomy, 20% of patients underwent distal pancreatectomy, 4% of patients underwent total pancreatectomy, and 32% patients underwent only ex-ploratory laparotomy and biopsy. At present the best way for pre-operative staging of pancreatic cancer is bolous and tri-phase helical computed tomography, which have been showen to be almost 100% accurate in predicting unresectable disease. Serum CA19.9 level in patients with unresectable tumor was highly significantly higher compared with that in patients with resectable tumor. Positive significant correlation between CA19-9 with total bilirubin, ALT and AST. Conclusion: CA19.9 is one of the tumor markers for pancreatic adenocarcinoma. It can be used as marker to identify pancreatic adenocarcinoma with limited sensitivity and spe-cificity. The use of CA19.9 in conjunction with modern imaging techniques may improve the characterization of resectability and categorization of 'borderline-resectable' tumours, however this biomarker alone does not possess enough predictive value. Most likely, as suggested by many others, a combination of biomarkers is needed in order to achieve acceptable sensitivity and specificity in a disease with non-specific symptoms and low incidence.