The invention provides a filter element of a smoking article having a longitudinal axis and adapted for filtration of mainstream smoke generated by the smoking article, the filter element including a first region extending along the longitudinal axis of the filter element and exhibiting a first pressure drop and a second region extending along the longitudinal axis of the filter element and exhibiting a second pressure drop lower than said first pressure drop, wherein the first and second regions are arranged in a side-by-side configuration such that both regions are visible in a cross-section of the filter element perpendicular to the longitudinal axis, and wherein mainstream smoke can move from the second region into the first region, and further comprising a smoke-altering material, such as an oxidation catalyst, positioned in the first region.