microRNAs are 22-nucleotide-long double-strand small RNAs, able to modulate gene expression at posttranscriptional level, degrading mRNA and/or impairing translation. They have been shown to regulate mRNA and protein abundance and to participate in many regulatory circuits controlling developmental timing, cell proliferation and differentiation, apoptosis and stress response. Notably, microRNA activity has been correlated to the pathogenesis of cancer; they are aberrantly expressed in solid and hematological tumors, suggesting that they could function as oncogenes or tumor suppressors. The emerging role of miRNAs in the carcinogenesis and tumor progression has provided opportunities for their clinical application in the capacity of cancer detection, diagnosis, and prognosis prediction. Here, we describe the experimental protocol used to isolate microRNAs from human tissues coming from head and neck, mesothelioma, and thymoma tumors in order to perform microarray and RT-qPCR experiments.