The current high-speed deployment rate of non-programmable Renewable Energy Sources (RES) is making transmission network planning activities more and more complex and affected by a high level of uncertainty. Because network investments are capital intensive and the lifetime of the infrastructure spans several decades, it may happen that when a new line is commissioned it is no longer the best option and it might be partially regarded as a stranded cost. There is an on-going debate on the selection of the more effective technologies that could contribute to system flexibility. This category doesn’t only include grid technologies, but also storage elements and flexible demand, both located in transmission or provided by opportunely aggregated distributed energy sources located in distribution networks. FlexPlanning aims at creating a new tool for optimizing transmission and distribution grid planning, considering the placement of flexibility elements as an alternative to traditional grid planning. This approach aims at helping to reduce overall power system costs i.e. infrastructure deployment and operation costs, the latter in terms of procurement of energy and system services. FlexPlan is going to take into account environmental impact and footprint (impact on air quality for thermal generation, carbon footprint, impact on landscape of new T&D lines). A pre-processing tool is also created to determine location, size and associated costs for storage and flexible demand candidates. The new planning tool is first validated and then used for analysing six detailed regional scenarios at 2030-2040-2050 in order to assess the potential role of storage and flexible resources. Pan-European scenarios are preliminarily elaborated in order to provide border conditions for the regional cases. Regulatory conclusions are drawn to analyse whether opportune incentivisation procedures could be put in place by the regulators wherever some consistent advantages are demonstrated.