Initially, patients with EGFR mutation positive NSCLC respond well to osimertinib, a third generation EGFR tyrosine kinase inhibitor (TKI), but eventually progress. Upon progression multiple resistance mechanisms have been described and new therapeutic strategies are being developed to target these resistance mechanisms. Thorough and complete osimertinib resistance analysis enables optimal treatment decision making and might identify new targets for molecular treatment, thereby potentially improving patient outcome.