Abstract Larger cities typically give rise to two opposite effects: tougher competition among firms and higher production costs. Using an urban model with substitutability of production factors and pro-competitive effects, I study product market responses to an increase in city population, land-use regulations and commuting costs. I show that those responses depend on the land intensity in production. If the input share of land is low, a larger city attracts more firms setting lower prices, whereas for an intermediate land share, city expansion increases both the mass of firms and product prices. For a high land share, the mass of firms decreases with city size while product price increases. Softer land-use regulations and/or lower commuting costs reinforce pro-competitive effects, making city residents better-off via lower product prices and broader diversity.