Liquid biopsy can quantify and qualify cell-free (cfDNA) and tumour-derived (ctDNA) DNA fragments in the bloodstream. CfDNA quantification and mutation analysis can be applied to diagnosis, follow-up and therapeutic management as novel oncologic biomarkers. However, some tumor-types release a low amount of DNA into the bloodstream, hampering diagnosis through standard liquid biopsy procedures. Several tumors, as such as brain, kidney, prostate, and thyroid cancer, are in direct contact with other body fluids and may be alternative sources for cfDNA and ctDNA. Non-blood sources of cfDNA/ctDNA useful as novel oncologic biomarkers include cerebrospinal fluids, urine, sputum, saliva, pleural effusion, stool and seminal fluid. Seminal plasma cfDNA, which can be analyzed with cost-effective procedures, may provide powerful information capable to revolutionize prostate cancer (PCa) patient diagnosis and management. In the near future, cfDNA analysis from non-blood biological liquids will become routine clinical practice for cancer patient diagnosis and management.