The performance of isolates of the ectomycorrhizal fungi Coltricia perennis, Laccaria bicolor, Lactarius hepaticus and Paxillus involutus originating from Scots pine stands was studied on solid media with different concentrations of ammonium, glycine and glucose as inorganic nitrogen, organic nitrogen and carbon source. Laccaria bicolor was able to grow on both ammonium- and glycine-containing media. Biomass and growth rate of L. hepaticus and P. involutus on media with ammonium were generally higher than on media with glycine as nitrogen source. Coltricia perennis did not clearly show preference for either ammonium or glycine. Fractal dimensions, calculated from the biomass and radii of the fungi, were in the range 1–3. Fractal dimensions provided extra information about the foraging strategy of mycelia not obtained from growth rate and biomass production measurements, but cannot replace those because the use of fractal dimensions alone may lead to misinterpretation.