An exhaust gas aftertreatment system for an internal combustion engine, said system comprising - an exhaust duct allowing a through-flow of exhaust gas; - a catalytic NOx converter arranged in the exhaust duct; - a fluid inlet arranged to introduce a liquid reductant into the exhaust duct upstream the catalytic NOx converter; - a plate structure comprising a plurality of reductant droplet impinging plates arranged in a row in a longitudinal direction of the exhaust duct so as to force at least a portion of the exhaust gas to flow in a zig-zag pattern along a portion of the exhaust duct and thereby bring about impingement of reductant droplets introduced into the exhaust duct on the impingement plates during operation of the internal combustion engine, wherein the plate structure comprises: - a reductant target space arranged in an upstream part of the plate structure, wherein the reductant target space forms a box-like structure comprising a first impingement plate, a second impingement plate downstream of the first impingement plate, and first and second side walls (37, 38) connecting the first and second impingement plates (31, 32), - wherein the fluid inlet and the reductant target space are arranged in relation to each other so that the reductant, when introduced into the exhaust duct, is introduced in a direction towards the first and second impingement plates (31, 32) between the first and second side walls (37, 38) and thus into the reductant target space, the plate structure being arranged such that a main part of the exhaust gas flow does not pass an opening of the reductant target space but flows at sides of the plate structure. - an exhaust duct allowing a through-flow of exhaust gas; - a catalytic NOx converter arranged in the exhaust duct; - a fluid inlet arranged to introduce a liquid reductant into the exhaust duct upstream the catalytic NOx converter; - a plate structure comprising a plurality of reductant droplet impinging plates arranged in a row in a longitudinal direction of the exhaust duct so as to force at least a portion of the exhaust gas to flow in a zig-zag pattern along a portion of the exhaust duct and thereby bring about impingement of reductant droplets introduced into the exhaust duct on the impingement plates during operation of the internal combustion engine, wherein the plate structure comprises: - a reductant target space arranged in an upstream part of the plate structure, wherein the reductant target space forms a box-like structure comprising a first impingement plate, a second impingement plate downstream of the first impingement plate, and first and second side walls (37, 38) connecting the first and second impingement plates (31, 32), - wherein the fluid inlet and the reductant target space are arranged in relation to each other so that the reductant, when introduced into the exhaust duct, is introduced in a direction towards the first and second impingement plates (31, 32) between the first and second side walls (37, 38) and thus into the reductant target space, the plate structure being arranged such that a main part of the exhaust gas flow does not pass an opening of the reductant target space but flows at sides of the plate structure.