The chemical composition, morphometric and qualitative nut characteristics were studied in four traditional sweet chestnut and hybrid varieties produced on private estates in the Lovran surroundings, on the eastern slopes of Mount Učka, under the specific conditions of the sub-Mediterranean climate. Seven morphological characteristics were measured, and 12 nut and kernel qualitative characteristics were estimated using standardized descriptors. In addition, the samples were analyzed for proximate constituents (moisture, crude fat, crude protein, ash and total carbohydrates) and macro- and micro-nutrients (K, Mg, Ca, Na, Mn, Fe, Zn and Cu). Significant differences between traditional sweet chestnut and hybrid varieties were found in almost all of the studied morphometric and chemical nut characteristics. In general, chestnuts of hybrid varieties were characterized by larger fruits with higher moisture, crude protein, potassium, magnesium, sodium, iron and copper contents than in traditional sweet chestnut varieties. On the other hand, nuts of traditional sweet chestnut varieties were richer in total carbohydrates and crude fat. In addition, the presence of raised stripes, a small hilar scar and transversally ellipsoid nut shape were found to be typical for the traditional sweet chestnut varieties. Overall, our results suggest that the traditional varieties of the sweet chestnut can be easily differentiated from the new modern hybrid varieties by both morphological and chemical characteristics of the nut, and because of these differences, these two groups of chestnut varieties can have different practical uses.