A disposable garment having a consumer-activated component that is expandable to improve the fit and function of the garment. The expandable component includes a compressed, resilient, expansible member disposed within a sealed, air-impermeable envelope. The expandable component can be activated so that the component expands in a direction toward the body of the wearer of the garment by the application of a tensile force on the garment to expose an opening in the envelope, to thereby admit air into the envelope and allow the compressed expansible element to expand to its substantially uncompressed condition. When expanded, the expansible element can define a collection chamber for waste matter, or it can provide closer contact between the garment and the body of the wearer at predetermined areas to improve the fit of the garment to the body of the wearer, or it can provide closer contact between the garment and the body of the wearer to position an absorptive member adjacent a body opening to improve the absorption by the absorptive member of waste bodily fluids. The garment can thus be a disposable diaper, a sanitary napkin, or the like.