Cities are key players in the reduction of CO2 emissions and in the fight against climate change because they consume around 80% of energy production worldwide. Since new urban developments have become residual among the overall city interventions, existing buildings need to be deeply renovated in terms of energy performance or demolished and substituted by high performance buildings to fulfil the CO2 reduction goals assumed by the EU. Existing buildings and urban fabrics need also to achieve higher performances in terms of statics and functional requisites and open spaces quality, thus increasing energy efficiency and the sustainability of the city as a whole. Urban densification, which become possible thanks to the adoption of density bonus rights or incentives, emerges as a credible response able to address energy saving issues at building scale and to help financing the interventions, but the overall sustainability and effectiveness of these measures risk to be neutralized if they are implemented without a clear strategy at urban scale. By analysing the experiences of two medium-sized cities in Emilia-Romagna Region in Italy, the article supports the thesis that energy-sensitive densification processes, to be effective in achieving deep energy reduction targets, should be conceived as a part of an integrated and broader urban strategy fostering a wider urban regeneration of the existing city. (C) 2017 Elsevier B.V. All rights reserved.