Background:/Aims: Pancreatic neuroendocrine tumors (PNET) are relatively rare. Here, we present clinical and pathological characteristics of PNETs to show a relationship between computed tomography (CT) imaging and the 2010 World Health Organization (WHO) classification. Methodology: We retrospectively reviewed the records of 41 PNET patients who were treated between 2002 and 2012. All tumors were classified as neuroendocrine tumor (NET) grade 1 (121), NET grade 2 (G2), or neuroendocrine carcinoma (NEC) grade 3 (G3) on the basis of the 2010 WHO classification system. Results: Twenty-five tumors were classified as G1, 11 as G2, and five as G3. Mean sizes of the G1, G2 and G3 tumors were 1.84 +/- 0.54, 4.90 +/- 0.84, and 5.62 +/- 1.18 cm, respectively, (P < 0.01). A PNET is typically hypervascular and exhibits contrast enhancement on enhanced CT. Higher percentage of G1 tumors demonstrated typical imaging and showed a significantly greater distinct mass compared with G2 and G3 tumors. Conclusions: Although PNET has many imaging features that appear on CT, G2 and G3 tumors often show atypical imaging features, particularly with large sizes and/or ill-defined features, when compared with G1 tumors. If a PNET has atypical imaging features, possibility of malignancy should be considered.