Since the activity of several conventional anticancer drugs is restricted by resistance mechanisms and dose-limiting side-effects, the design of nanocarriers seems to be an efficient and promising approach for drug delivery. Their chemical and mechanical stability and their possible multifunctionality render tubular nanomaterials, such as carbon nanotubes (CNTs) and carbon nanofibres (CNFs), promising delivery agents for anticancer drugs. The goal of the present study was to investigate CNTs and CNFs in order to deliver carboplatin in vitro.No significant intrinsic toxicity of unloaded materials was found, confirming their biocompatibility. Carboplatin was loaded onto CNTs and CNFs, revealing a loading yield of 0.20 mg (CNT-CP) and 0.13 mg (CNF-CP) platinum per milligram of material. The platinum release depended on the carrier material. Whereas CNF-CP marginally released the drug, CNT-CP functioned as a drug depot, constantly releasing up to 68% within 14 days. The cytotoxicity of CNT-CP and CNF-CP in urological tumour cell lines was dependent on the drug release. CNT-CP was identified to be more effective than CNF-CP concerning the impairment of proliferation and clonogenic survival of tumour cells. Moreover, carboplatin, which was delivered by CNT-CP, exhibited a higher anticancer activity than free carboplatin.