The paper considers how product liability may shape firm size, product specification choices and market structure. We introduce a spatial Cournot duopoly on the linear market, where firms make an initial decision of product differentiation, then invest in precaution, before competing in quantity. Our main results are fourfold; 1) with full coverage of the market by the duopoly, there exist two equilibria (in pure strategies): central agglomeration (which is stable for low liability costs), and dispersion (which is stable for not too large liabiliy costs); 2) for larger liability costs, a mixed market structure duopoly/monopoly sustains a unique equilibrium with product differentiation; 3) this equilibrium enables a scope of differentiation higher (smaller) than the full duopoly (the social optimum); 4) the impact of liability costs on firms size and profits is complex, since it depends on the impact on both product differentiation and market structure. Finally, we show that consumer surplus and social welfare are both higher under the mixed market structure than under the full duopoly in an equilibrium with product differentiation.