Background/Aims: Circulating tumor cells (CTCs) are valuable in both basic research and clinical application for cancer management. In the current study, we evaluated the diagnostic value of CTCs in pancreatic ductal adenocarcinoma (PDAC). Methods: In total, 143 blood samples from 95 consecutively diagnosed PDAC patients and 48 healthy donors were collected. Combined data from immunostaining of CD45, DAPI and fluorescence in situ hybridization (FISH) with chromosome 8 centromere (CEP8) probe were used to identify CTCs. Cells with features of CD45-/DAPI+/CEP8>2 were detected as CTCs. Results: CTCs were classified as triploid, tetraploid and multiploid based on chromosome 8 copy number. CTC subtype composition was significantly different among groups. Both subtype number and total CTC number were significantly increased in PDAC patients, compared to healthy controls. Total CTC number had 75.8% sensitivity and 68.7% specificity at a cutoff value of 2 cells/3.2 mL. This study is the first to report that CTC subtype number is also useful in cancer diagnosis. Sensitivity was 53.7% and specificity was 85.4% at a cutoff point of 2 CTC subtypes. The diagnostic value of both total CTC number and CTC subtype number was a little poorer than CA199. Conclusions: Both CTC subtype and total CTC number may serve as potential biomarkers for PDAC.