The CH‐oxidative activity of Wolfiporia cocos cultures of different ages was studied utilizing diamondoid derivatives as conformationally rigid models. Adamantane‐1‐ol and 1‐bromoadamantane, traditional precursors for the synthesis of polysubstituted adamantanes, gave qualitatively similar reaction mixtures in which adamantane diols dominated. While the reactions occurred with high preparative yields, the biotransformation does not display clear differences from classic electrophilic or radical adamantane functionalization reactions. In contrast, the fungal oxidation of diamantane‐4‐ol occurred with unexpected selectivity yielding diamantane‐4,9‐diol and diamantane‐1,9‐diol. The latter product is quite uncharacteristic for diamantane chemistry because the most deactivated CH‐position is attacked. To elucidate the active fungal component, additional experiments were performed with supernatant and resting cells harvested at various culture ages. Oxidative activity was detected in resting cells from 4‐ and 6‐day‐old cultures in pure water medium, and from 6‐day‐old cultures in buffer at pH 2, but disappeared at higher pH values.