Patients with non-small cell lung cancer with specific mutations for which so-called 'targeted therapy' is available are likely to have a favourable tumour response. The first patient, a man aged 64 with an activating epidermal growth factor receptor (EGFR) mutation, had a longstanding tumour response on erlotinib, an EGFR tyrosine kinase inhibitor (TKI). After 16 months on treatment, there was still no progression of the disease. The next patient, a woman aged 78, also responded favourably to erlotinib After 2.5 years she discontinued the medication and the disease recurred. Remission was induced again with the use of erlotinib, but the recovery was of short duration and she died a few months later. A third patient, a 66-year-old man, developed resistance to erlotinib due to a T790M mutation in the EGFR protein. He responded well to a combination of the irreversible EGFR-TKI afatinib and the antibody to EGFR, cetuximab. The final patient, a 47-year-old woman, had an EML4-ALK translocation and responded remarkably well to an ALK inhibitor, crozotinib. Mutation analysis should be carried out in all patients with metastatic adenocarcinoma or large cell lung cancer, specifically for genes for which a targeted therapy is already available.