Type 2 diabetes mellitus (T2DM) is a polygenetic disorder resulting from interaction of both hereditary and environmental factors. Diet is an important environmental factor in the development of T2DM. However, there existed inconsistent conclusions among previous studies. The validity of a study of associations between diet and diabetes depends on the method used in the study. Associations between individual nutrients/foods and T2DM have been explored even till today, but the controversy is still unsolved due to the limitations of the study methods such as interactions among nutrients. Emergence of analyses on dietary patterns and diabetes shows its popularity in the studies of associations of dietary patterns with T2DM, but only a few articles have been published. In this review, dietary-pattern-related studies since 1990 were identified by searching through Medline and PubMed in order to analyze methods used in the studies of diabetes. A dietary pattern approach was introduced as an alternative complementary way used to test associations of diet with risk of T2DM and the advantages of the studies of T2DM using this new approach are also explored. It is concluded that the dietary pattern approach shows its advantages over that using individual nutrients or foods in studies on associations between the diet and diabetes, but its reproducibility and validity for such effects, however, need to be further verified in different ethnic population-based on diverse eating habits. The long-term effects of a beneficial dietary pattern on T2DM also require clarifying in future studies.