According to current Polish and international recommendations, detection of EGFR gene somatic mutations is the essential part of routine diagnostic algorithm in advanced NSCLC patients considered for tyrosine kinase inhibitor therapy. Molecular heterogeneity of tumor tissue and cytology materials used for molecular diagnostics is challenging for classic methods of genetic analysis, such as Sanger sequencing, driving the development and implementation of specialized, highly sensitive techniques for mutations detection. Constant, dynamic progress in molecular biology techniques, particularly development of next-generation sequencing, should enable clinical implementation of simultaneous multiple therapeutic biomarkers analysis as well as non-invasive EGFR mutations diagnostic based on free-circulating DNA isolated from blood of non-small cell lung cancer patients.