Novel 6-Cycloalkyl-pyrazolopyrimidinones according to formula (I) with PDE9 inhibiting properties, wherein R 1 is a 5 or 6 membered aromatic heteroaryl-group, R 2 is an optional substituent, D is optionally substituted cyclopentyl, cyclohexyl, tetrahydrofuranyl, tetrahydropyranyl or 2-, 3- or 4-pyridyl, m= 1 or 2 and n is 0, 1 or 2. The new compounds can be used as medicaments, in particular for the treatment of conditions concerning deficits in perception, concentration, learning or memory. Such conditions may be associated with Alzheimer's disease, schizophrenia and other diseases. The new compounds can be used in the treatment of cognitive impairment associated with such diseases.
