The present invention relates to novel pyrimidine derivatives of formula (I)[Formula should be entered here] as inhibitors of the enzyme phosphodiesterase 10 (PDE-10), pharmaceutical compositions comprising an effective amount of these compoundsand theuse of the compounds for manufacturing a medicamentfor thetreatment ofpathological conditions or diseases that can improve by inhibition of the enzyme Phosphodiesterase such as neurological, psychiatric, respiratory or metabolic diseases.