Image guide radiotherapy with the Cone Beam CT kV (CBCT-kV) developed by Elekta has been implemented at the centre Léon Bérard in November 2006. The treatment procedure is presented and detailed for prostate cancer IGRT and non small cell lung cancer (NSCLC) stereotactic radiotherapy (SRT). CBCT-kV is routinely used for SRT, selected paediatric cancers, all prostate carcinomas, primitive brain tumours and head and neck cancers that do not require nodes irradiation. Thirty-five to 40 patients are treated within a daily 11-hours period. The general procedure for 3D images acquisition and their analysis is described. The CBCT-kV permitted to identify about 10% of prostate cancer patients for whom a positioning with bone-based 2D images only would have led to an unacceptable dose distribution for at least one session. SRT is now used routinely for inoperable NSCLC. The easiness of implementing CBCT-kV imaging and its expected medical benefit should lead to a rapid diffusion of this technology that is also submitted to prospective and multicentric medico-economical evaluations.