Environmental impacts due to urbanisation are increasingly affecting human well-being. Urban metabolism consistently contributes to environmental pollution and degradation, while existing green infrastructures are often insufficient to counterbalance these pressures through the supply of ecosystem services. In this context, this study proposes a novel framework that integrates ecosystem service accounting and Life Cycle Assessment to quantify the mismatch between ecosystem services supply and demand in urban systems. This approach was applied in two study areas (Province of Salerno and Naples, Southern Italy), selected as representative case studies with different urban and environmental profiles. Regulating ecosystem services provided by urban tree vegetation, including air pollution removal, carbon sequestration, and avoided runoff, were assessed using the i-Tree Canopy software. These services were quantified in both biophysical and economic terms to account for ecosystem services supply. In parallel, the Life Cycle Assessment methodology was used to evaluate the environmental impacts associated with urban metabolism, which were used as proxies for ecosystem services demand. Results highlighted marked differences between the two Provinces. Salerno exhibited a significantly higher tree cover (63.4%) compared to Naples (24.4%), as well as a greater potential for additional plantable areas. The ecosystem services supply in Salerno was higher, with carbon sequestration notably exceeding the demand, thus resulting in a surplus. In contrast, Naples showed a critical imbalance, with the current carbon sequestration ecosystem service supply meeting only about 4% of the estimated demand. The total economic value of the regulating ecosystem services of the two Provinces amounted to about 13.5 billion euros per year. In conclusion, the proposed integrated approach offers a replicable and scalable tool for identifying spatial mismatches in ecosystem services supply and demand. It can support urban planners and policy-makers in enhancing green infrastructure strategies and advancing sustainability goals in urban areas.