T1 tumors have the best prognosis among primary non-small-cell lung cancers, basically because surgery is generally possible. Among 5.667 patients with primary lung cancer included in the KBP-2000-CPHG study, we examined the characteristics of 419 T1 tumors, i.e. 9.2% of the non-small-cell cancers. Compared with the group of patients with non-T1 tumors, patients with T1 tumors were younger (p=0.0007). They had an equivalent percentage of squamous-cell tumors but more adenocarcinomas (40.3% versus 35.5%, p=0.05). TNM staging showed that 27.6% of the T1 tumors were metastatic at diagnosis (stage IV) with 12.4% T1N0M1 nad 15.2% T1N1-3M1. For the M0 tumors, 52.2% were T1N0 (stage IA) and 20.1% were T1N1-3. Squamous-cell tumors were significantly more frequent among the T1M1 tumors (p=0.07). More than one quarter (27.6%) of the T1 tumors were in stage IV, pointing out the importance of the initial work-up. This findings suggests we should revisit strategies in order to take into account new diagnostic possibilities. Likewise for the therapeutic strategy. Combinations using chemotherapy, surgery and radiotherapy should be better defined for this group of tumors.