A wall-flow honeycomb filter comprising a ceramic monolith having a plurality of porous walls formed therein. The plurality of porous walls define a plurality of inlet cells and a plurality of outlet cells extending between an inlet end face and an outlet end face of the monolith. The inlet cells are open at the inlet end face and plugged at or near the outlet end face. The outlet cells are open at the outlet end face and plugged at or near the inlet end face. The monolith has a ratio of a combined cross-sectional area of the inlet cells to a combined cross-sectional area of the outlet cells greater than 1. The monolith has at least one inlet cell cluster which contains an N×M group of inlet cells, N and M being integers greater than 1, each inlet cell cluster consisting of a plurality of inlet cells separated by inlet cluster walls.