Methodologies usually adopted in urban and regional planning do not assume an approach based on Spatial Data Infrastructures principles, which could ensure a better use of geospatial data and support interoperability of planning choices providing an active participation of stakeholders involved in planning processes. An innovative approach of e-government based on a better organization and management of geospatial data, could contribute, through a deeper territorial knowledge and a more appropriate use of decision support tools, to more effectively pursue planning goals. Spatial planning and related information have a strategic importance not only at local and national level but also at international scale where a "continuum" of settlements characterizes the crossing of various countries. Planning activity is also strictly related to aspects such as management of natural resources, prevention of natural disasters, transports which in many cases have international cross-border interests. Consequently, today there is an absolute need of harmonized planning data a strong demand of planning core data sets in order to provide an easy and wide understandability of this information. The objective of the Plan4all project is to build a network of local, regional and national stakeholders, companies in the ICT sector, organizations involved in planning and economic development, universities and international agencies in order to find a consensus concerning the harmonization of spatial planning data based on existing best practices in Europe and according to the European Directive INSPIRE. The project takes into account lessons learned from previous experiences, such as Armonia, Humboldt, eSDINet+, Euradin, whose partners are also present in the Plan4all consortium. The project will involve also the experience of OGC working group members concerning the definition of standards technologies. Plan4all aims to contribute to the harmonization of planning data. Based on best practi- - ces analysis, the project is producing a series of technical documents for metadata profiles design and implementation, data models and harmonization procedures. Particular attention will be paid to issues related to the protection of intellectual property rights, as well as security aspects.