The present invention relates to novel 1,2,4-triazolo[4,3-a]pyridine compounds of formula (I) as positive allosteric modulators (PAMs) of the metabotropic glutamate receptor subtype 2 ("mGluR2"). The invention is also directed to pharmaceutical compositions comprising such compounds, to processes for preparing such compounds and compositions, and to the use of such compounds and compositions for the prevention or treatment of disorders in which mGluR2 subtype of metabotropic receptors is involved.