Densified fiber structures are incorporated into mattress constructions and bedding Applications. In one embodiment, a mattress innerspring is combined with one or more densified fiber structures which fit with the innerspring and with other components of the mattress. An innerspring perimeter support made of densified fiber may encase the outer perimeter of the innerspring and provide structural side walls to the mattress. In another embodiment and application, the inner cavity of one or more coils of a mattress innerspring may be substantially filled with densified fiber. In yet another embodiment, the general space between the coils of the innerspring may be filled with densified fiber. In still another embodiment, a combination of densified fiber supports may be included in one mattress innerspring assembly, such as, for example, a densified fiber perimeter support with densified fiber filled innerspring coils, or a densified fiber perimeter support with densified fiber filled in the general space between the coils of the innerspring, or a densified fiber filled innerspring coils densified fiber in the general space between each innerspring coil. Additional densified fiber components for use in a mattress innerspring include an innerspring corner coil reinforcement member which is made of densified fiber and which fits around the coils located at each of the four corners of the innerspring.