The invention relates to particular crystalline forms of 2-methyl-2-[4-(3-methyl-2-oxo-8-quinolin-3-yl-2,3-dihydro-imidazo[4,5-c]quinolin-1-yl)-phenyl]-propionitrile, its hydrates and solvates, its salts and hydrates and solvates of its salts, certain processes for their preparation, pharmaceutical compositions containing these crystalline forms, and their use in diagnostic methods or, preferably, for the therapeutic treatment of warm-blooded animals, especially humans, and their use as an intermediate or for the preparation of pharmaceutical preparations for use in diagnostic methods or, preferably, for the therapeutic treatment of warm-blooded animals, especially humans.