Establishing the relevant product market is a key issue in monopolization cases because the way a market is defined can determine whether a firm has monopoly power.

The definition of the relevant product market is crucial in monopolization cases because it helps determine the boundaries within which competition is assessed. If a market is defined too narrowly, a firm might appear to have monopoly power; if defined too broadly, the same firm might seem to face significant competition. Thus, the market definition can significantly influence the outcome of whether a firm is considered to have monopoly power.