Substituted pyrazolopyrimidine derivatives of formula (I) wherein R.sup.1 represents chloro or bromo; R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6 and R.sup.7 independently represent e.g. hydrogen or C.sub.1-6-alkyl; R.sup.8 represents a radical R.sup.9 or a radical R.sup.10, whereby one of the two radicals R.sup.8 represents R.sup.9 and the other radical R.sup.8 represents Ret; R.sup.9 represents e.g. a phenyl or thiophene group, and R.sup.10 represents e.g. hydrogen or methyl; are potent mGluR5 modulators and are useful for the prevention of acute and chronic neurological disorders.