The Euros 32.5bn project is split into Euros 20.5bn for new lines and Euros 12bn for improving existing infrastructure. New construction will be funded by the French government (Euros 4bn), special taxes (Euros 6bn), local authorities (Euros 0.9bn), and a loan of Euros 9bn.

Grand Paris Express comprises three lines. The 95km Euros 17.5bn Red Line will encircle Paris running clockwise from Le Bourget via Chelles, Noisy-Champs, Champigny, Villejuif, Issy, Nanterre, La Défense, and St Denis Pleyel to Le Bourget with a branch from there to Roissy Charles de Gaulle Airport and Le Mesnil-Amelot.

The 30km Euros 1bn Blue Line will involve extending the automatic Line 14 of the Paris metro north from St Lazare via St Ouen to St Denis Pleyel and south from Olympiades via Villejuif to Orly Airport.

The 50km Euros 2bn Green Line will follow an arc through the western suburbs, and will run from Orly Airport via Massy-Palaiseau, St Quentin, and Versailles to Nanterre, although the Versailles - Nanterre section will not be completed until after 2025.

In the longer term, lines from St Denis Pleyel to Bobigny, Rosny, Noisy-Champs and Champigny Centre are planned. Grand Paris Express will also serve three proposed TGV stations at St Denis Pleyel, Nanterre and Orly Airport.