The utility of endoscopic ultrasound fine‐needle aspiration cytology (EUS‐FNAC) or endoscopic ultrasound fine‐needle aspiration biopsy (EUS‐FNAB) for diagnosis of small and large pancreatic ductal adenocarcinomas (PDACs) remains in question. We addressed this by analyzing 97 definitively diagnosed cases of PDAC, for which both EUS‐FNAC and EUS‐FNAB had been performed. We subclassified the 97 solid masses into small (n = 35) or large (n = 62) according to the maximum tumor diameter (<24 mm or ≥24 mm) and compared the diagnostic sensitivity (truly positive rate) of EUS‐FNAC and of EUS‐FNAB for small and large masses. Diagnostic sensitivity of EUS‐FNAC did not differ between large and small masses (79.0% vs. 60.0%; p = 0.0763). However, the diagnostic sensitivity of EUS‐FNAB was significantly higher for large masses (85.5% vs. 62.9%; p = 0.0213). Accurate EUS‐FNAC‐based diagnosis appeared to depend on the degree of cytological atypia of cancer cells, which was not associated with quantity of cancer cells. The accuracy of EUS‐FNAB‐based diagnosis appeared to depend on cancer cell viability in large masses and cancer volume in small masses. Based on the advantages or disadvantages in each modality, both modalities play an important role in the qualitative diagnosis of PDAC as a complementary procedure.