A surface treating appliance includes a first cyclonic separating unit including at least one first cyclone, a second cyclonic separating unit including a plurality of second cyclones arranged in parallel about an axis, and a third cyclonic separating unit including a plurality of third cyclones arranged in parallel about the axis. Each of the second cyclones and the third cyclones has a tapering body with an outside wall. The plurality of third cyclones is divided into at least a first set of third cyclones and a second set of third cyclones, each of the plurality of second cyclones and the first set of third cyclones being arranged about the second set of third cyclones. At least a part of the outside wall of each of the plurality of second cyclones and each of the first set of third cyclones forms part of the external surface of the surface treating appliance.