Efficiency of solid and liquid inocula and their use for spawn production were compared so that improved cultivation conditions for the edible mushroom Pleurotus ostreatoroseus could be tested. Solid and liquid inocula were prepared respectively with Potato Dextrose Agar (PDA) and Liquid Potato Dextrose (LPD). Wheat grains and cotton residues were used as substrates for spawn preparation. Inoculum types did not affect the development of P. ostreatoroseus, and LPD spawns were cheaper, more homogenous, less contaminated. Decomposition activity of mushroom growth, as a percentage of organic matter loss (OML), was higher in the wheat grain spawn and was not influenced by the inoculum type. Advantages in the use of cotton residue for spawn production were longer storage time, lower contamination and reduced costs. The cotton residue substrate may be also used for the production of mushroom fruiting bodies.