microRNAs (miRNAs) can act as oncosuppressors or oncogenes, induce chemoresistance or chemosensitivity, and are major posttranscriptional gene regulators. Anaplastic lymphoma kinase (ALK), EGF receptor (EGFR), and V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) are major drivers of non-small cell lung cancer (NSCLC). The aim of this study was to assess the miRNA profiles of NSCLCs driven by translocated ALK, mutant EGFR, or mutant KRAS to find driver-specific diagnostic and prognostic miRNA signatures. A total of 85 formalin-fixed, paraffin-embedded samples were considered: 67 primary NSCLCs and 18 matched normal lung tissues. Of the 67 primary NSCLCs, 17 were echinoderm microtubule-associated protein-like 4-ALK translocated (ALK + ) lung cancers; the remaining 50 were not (ALK − ). Of the 50 ALK − primary NSCLCs, 24 were EGFR and KRAS mutation-negative (i.e., WT; triple negative); 11 were mutant EGFR (EGFR + ), and 15 were mutant KRAS (KRAS + ). We developed a diagnostic classifier that shows how miR-1253, miR-504, and miR-26a-5p expression levels can classify NSCLCs as ALK-translocated, mutant EGFR, or mutant KRAS versus mutation-free. We also generated a prognostic classifier based on miR-769-5p and Let-7d-5p expression levels that can predict overall survival. This classifier showed better performance than the commonly used classifiers based on mutational status. Although it has several limitations, this study shows that miRNA signatures and classifiers have great potential as powerful, cost-effective next-generation tools to improve and complement current genetic tests. Further studies of these miRNAs can help define their roles in NSCLC biology and in identifying best-performing chemotherapy regimens.N on-small cell lung carcinoma (NSCLC) includes adenocarcinomas and squamous cell carcinomas (1), which mainly are treated surgically, although chemotherapy is used both preoperatively (neoadjuvant chemotherapy) and postoperatively (adjuvant chemotherapy), with or without radiotherapy (2, 3). The best-characterized oncogenes that drive NSCLC are anaplastic lymphoma kinase (ALK), EGF receptor (EGFR), the V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), the protooncogene receptor tyrosine kinase MET, and the recently identified receptor tyrosine kinase of the insulin receptor family ROS1. Knowledge of their mutational status is of key importance in choosing the most efficient chemotherapy regimen (4).Recent clinical trials have shown that patients presenting with NSCLCs driven by EGFR and ALK gene rearrangements benefit from chemotherapies based on specific tyrosine kinase inhibitors (TKIs), such as EGFR-TKI and crizotinib, respectively. Despite the wide number of recently developed drugs, none targets mutant KRAS, although the inhibition of the downstream signaling component Ras-Raf-Erk seems to be a possible approach (2, 5). microRNAs (miRNAs) are small, noncoding RNAs that are deregulated in malignancies (5) and can act as oncogenes or oncosuppressors (6); their deregulation also can i...