Patient-derived tumour xenografts and tumour organoids have become important preclinical model systems for cancer research. Both models maintain key features from their parental tumours, such as genetic and phenotypic heterogeneity, which allows them to be used for a wide spectrum of applications. In contrast to patient-derived xenografts, organoids can be established and expanded with high efficiency from primary patient material. On the other hand, xenografts retain tumour-stroma interactions, which are known to contribute to tumorigenesis. In this review, we discuss recent advances in patient-derived tumour xenograft and tumour organoid model systems and compare their promises and challenges as preclinical models in cancer research.