Spruce and larch wood are wood species which are, in the form of solid wood most frequently used for building, construction so as lumber. Therefore besides the mechanical properties of wood, durability of wood is also very important. It is known that spruce wood is classified as non-durable, while larch wood is classified as moderately durable. Furthermore, at both tree species it is well known that mechanical properties and ring width (density) are correlated. The impact of ring-widths on natural durability of wood and ratio of extractives, which generally provide natural durability of wood, was researched. Therefore, wood samples of spruce and larch with different ring-widths were prepared. Some specimens were extracted prior the exposure to different wood decay fungi (SIST EN 113) to determine the portion of extractives for individual class of rings-widths. The results showed that ring-width in both wood had no effect on the portion of extractives in wood. Gravimetrically determined mass loses of the specimens showed that tree-ring widths of both tested species did not have the impact on fungal decomposition.