The ITU's work is organized according to three "Sectors", which build and shape tomorrow's networks and services.

The Radiocommunication Sector (ITU-R):

• Draws up the technical characteristics of terrestrial and space-based wireless services and systems
• Develops operational procedures.

The Telecommunication Standardization Sector (ITU-T):

• Prepares the technical specifications for tele-communication systems, networks and services (including their operation, performance and maintenance).
• Establishes tariff principles and accounting methods used to provide international service.

The Telecommunication Development Sector (ITU-D) advises developing countries on "best business practices" for development strategies and network management policies.

189 Member States (countries); more than 600 Sector Members (corporations and organizations)

Membership of ITU is open to governments, which may join the Union as Member States, as well as to private organizations like carriers, equipment manufacturers, funding bodies, research and development organizations and international and regional telecommunication organizations, which can join ITU as Sector Members. Member States may vote.

Majority vote of the Member States.

In practice, decisions are taken by consensus.

Through Plenipotentiary 1998 Resolution 101: Internet Protocol (IP)-based networks the members encouraged "ITU-T to continue its collaborative activities on IP-based networks with ISOC/IETF" and "all Sectors to consider their future work programmes on IP-based networks;" they also resolved "that ITU shall fully embrace the opportunities for telecommunication development that arise from the growth of IP-based services," among other things.