Radiomics is a process of extraction and analysis of quantitative features from diagnostic images. Liquid biopsy is a test done on a sample of blood to look for cancer cells or for pieces of tumourigenic DNA circulating in the blood. Radiomics and liquid biopsy have great potential in oncology, since both are minimally invasive, easy to perform, and can be repeated in patient follow-up visits, enabling the extraction of valuable information regarding tumour type, aggressiveness, progression, and response to treatment. Both methods are in their infancy, with major evidence of application in lung and gastrointestinal cancer, while still undergoing evaluation in other cancer types. In this paper, the main oncologic applications of radiomics and liquid biopsy are reviewed, and a synergistic approach incorporating both tests for cancer diagnosis and follow-up is discussed within the context of systems medicine. TEACHING POINTS: • Radiomics is a process of extraction and analysis of quantitative features from diagnostic images. • Most clinical applications of radiomics are in the field of oncologic imaging. • Radiomics applies to all imaging modalities. • A cluster of radiomic features is a "radiomic signature". • Machine learning may improve the efficacy of radiomics analysis.