There is provided a smoking article comprising a filter. The filter comprises a hollow tube having an inner surface. The filter further comprises a flow restrictor disposed in the hollow tube, and adapted to divert at least a portion of the flow of mainstream smoke between an outer surface of the restrictor and the inner surface of the hollow tube. Furthermore, the filter comprises a retaining element disposed downstream of the flow restrictor, the retaining element having one or more openings. Each of the openings of the retaining element has at least one cross-sectional dimension that is smaller than the smallest cross-sectional dimension of the flow restrictor to prevent the flow restrictor from moving downstream of the retaining element. The flow restrictor is substantially spherical, at least one cross-sectional dimension of the one or more openings of the retaining element being smaller than the diameter of the flow restrictor.