<p>Androgen deprivation therapy (ADT) is widely used for prostate cancer (PCa) treatment. However, this treatment is not curative, and PCa progresses despite ADT, becoming castration-resistant (CR). Castration-resistant prostate cancer (CRPCa) is a highly aggressive form of PCa that progresses, metastasizes, and develops treatment resistance rapidly. MiRNAs are known to be involved in cancer development mechanisms, including cell cycle regulation, apoptosis, angiogenesis, and epithelial-mesenchymal transition. The aim of the present work was a comparative analysis of the expression of 14 miRNAs involved in PCa development in hormone-sensitive prostate cancer (HSPCa) patients before any treatment, after ADT, in CRPCa, as well as in healthy donors (HD), to assess their diagnostic potential for CR. 44 differentially expressed miRNA ratios were found in urine extracellular vesicles (EVs), 41 in cell-free urine, and 35 in plasma EVs. ROC curve analysis was performed using three different control groups: HD + HSPCa, HSPCa, and HSPCa under maximal androgen blockade (MAB) treatment. For each biofluid and control group, the most diagnostically effective miRNA ratios were evaluated to identify minimal and redundant diagnostic panels. Urine EVs provided the most diagnostically efficient miRNA ratios and panels. For the HD + HSPCa control group, the minimal panel consisting of 3 miRNA ratios was able to diagnose 95% of CRPCa patients, while a partially redundant panel of 5 miRNA ratios diagnosed 90% of CRPCa patients at least twice. For the HSPCa control group, two minimal panels consisting of 2 miRNA ratios each were able to diagnose 100% of CRPCa patients, and a redundant panel of 6 different miRNA ratios also diagnosed 100% of CRPCa patients at least twice. For the MAB control group, a minimal panel of 3 miRNA ratios diagnosed 100% of CRPCa patients, and a partially redundant panel consisting of 4 different miRNA ratios diagnosed 95% of CRPCa patients.</p>