The present invention relates to four distinct crystalline forms and to an amorphous form of [4-(3-Fluoro-5-trifluoromethyl-pyridin-2-yl)-piperazin-l-yl]-[5-methanesulfonyl-2-((S)-2,2,2-trifluoro-1-methyl-ethoxy)-phenyl]-methanone, and to their use in the preparation of pharmaceutical compositions. The compounds of present invention are suitable for the preparation of a medicament useful for treating psychoses, pain, neurodegenerative disfunction in memory and learning, schizophrenia, dementia and other diseases in which cognitive processes are impaired, such as attention deficit disorders or Alzheimer's disease.
