Common buckwheat and Tartay buckwheat are the most extensively cultivated and consumed Fagopyrum species worldwide. The evaluation of grain size characteristics and nutritional properties of different buckwheat varieties plays an important role in their effective utilisation and dissemination. Eleven buckwheat varieties (ten common, one Tartary) were cultivated in north-eastern Slovenia under Central European growing conditions in two consecutive years. Whole grain characterization included various physical properties (TGW – thousand-grain weight, R-width, R-length, L/W ratio), determination of total phenolic compounds (TPC) and multi-element analysis. The TGW ranged from 12.3–29.4 g, the grain length from 4.1–6.8 mm and the grain width from 2.8–5.3 mm, while the mean L/W ratio reached 1.44. According to the TGW, buckwheat varieties were divided into four groups, two groups based on grain length and three groups based on grain width. Under the given growing conditions, the Billy variety developed the largest grains in both years and La Harpe and Doris the smallest grains. The TPC varied between 4.4 and 15.3 mg GAE g-1 and was significantly higher in the Tartary buckwheat variety. The content of macro- (K, Mg, P, Ca, S) and microelements (Na, Cr, Mn, Fe, Co, Cu, Zn, Mo) varied considerably between these varieties. The highest coefficients of variation were found for Fe (51.4%), TPC (39.9%), Ca and Co (34.4%) and Cr (32.9%). A very strong positive significant Pearson correlation (≥0.80) was observed for eight pairs of variables. The present evaluation of buckwheat varieties revealed considerable diversity in the traits studied under Central European conditions.