An exhaust-gas aftertreatment system for nitrogen oxide and particle reduction in internal combustion engines, wherein the nitrogen oxide reduction is effected by means of a catalytic converter and the particle reduction is effected by means of a particle filter, and wherein - a particle filter (5, 9, 9'), through which the exhaust gas flows, is arranged in the exhaust-gas stream of the internal combustion engine, - the particle filter (5, 9, 9') is a ceramic filter, - the particle filter (5, 9, 9') has a greater geometrical surface area on its outflow side than on the inflow side, - the particle filter (5, 9, 9') is laden with a catalyst material for reducing nitrogen oxides at least in the region of the greater geometrical surface area, - the greater geometrical surface area of the particle filter (5, 9, 9') on the outflow side is formed by specific shaping of the filter material and/or by fixtures (23, 23'), - the particle filter (5, 9, 9') is produced by extrusion and has parallel ducts, characterized in that - the cell densities vary over the cross section of the particle filter (5, 9, 9'), - regions of high cell density adjoin regions of low cell density, - the regions of high cell density are closed towards the inflow side and are open towards the outflow side, - the regions of low cell density are closed towards the outflow side and are open towards the inflow side, - the exhaust gas flowing onto the particle filter (5, 9, 9') passes via the inflow-side openings into the regions of low cell density, flows over through the duct walls into the regions of high cell density and from there flows via the outflow-side openings out of the particle filter (5, 9, 9'), - at least the outflow side of the particle filter is laden with a catalyst material for NO x reduction. - a particle filter (5, 9, 9'), through which the exhaust gas flows, is arranged in the exhaust-gas stream of the internal combustion engine, - the particle filter (5, 9, 9') is a ceramic filter, - the particle filter (5, 9, 9') has a greater geometrical surface area on its outflow side than on the inflow side, - the particle filter (5, 9, 9') is laden with a catalyst material for reducing nitrogen oxides at least in the region of the greater geometrical surface area, - the greater geometrical surface area of the particle filter (5, 9, 9') on the outflow side is formed by specific shaping of the filter material and/or by fixtures (23, 23'), - the particle filter (5, 9, 9') is produced by extrusion and has parallel ducts, - the cell densities vary over the cross section of the particle filter (5, 9, 9'), - regions of high cell density adjoin regions of low cell density, - the regions of high cell density are closed towards the inflow side and are open towards the outflow side, - the regions of low cell density are closed towards the outflow side and are open towards the inflow side, - the exhaust gas flowing onto the particle filter (5, 9, 9') passes via the inflow-side openings into the regions of low cell density, flows over through the duct walls into the regions of high cell density and from there flows via the outflow-side openings out of the particle filter (5, 9, 9'), - at least the outflow side of the particle filter is laden with a catalyst material for NO x reduction.