High speed broadband creates potential productivity gains and has a positive impact on economic growth. Achieving Europe’s broadband access objectives will require large scale investment in next generation broadband networks, and it is imperative that an appropriate investment climate is created to encourage fibre network rollout. This study considers whether and how competition in the DSL market affects the incentives of operators to invest in the deployment of high-end fibre optic networks. Most earlier research on the drivers of investment in broadband technology has focused on the effect of mandatory access policies, such as local loop unbundling, or competing infrastructures. We posit that competition in the DSL sector may also influence fibre penetration, possibly to a considerable extent. We find that the relationship between service-based competition and fibre penetration is non-linear: a lack of or severe DSL competition is correlated with a negative effect on fibre penetration, but if a moderate degree of competition is already present in the market, more service-based competition may positively influence fibre penetration. The scale of these effects however varies with the openness of the DSL market: operators’ incentives to invest in fibre appear to be more sensitive to changes in DSL competition if there is extensive local loop unbundling.