Developing an accurate and accessible radiotherapy treatment method is a core challenge in medical physics today. Achievements in high-gradient accelerator technology (in the area of linear colliders) in the last decades have led to a proposal of using very high energy electrons (VHEE) in the energy range 50 - 250 MeV for deep-seated tumour radiotherapy. Previous studies with VHEE beams have shown promising features that could be beneficial in radiotherapy, such as significantly higher dose rate and dose reach that is better suited to treat deep-seated tumors compared to photons. However, studies with VHEE beams are still very limited and there are several concerns that need to be addressed, such as the relatively large entrance dose and large lateral scattering compared to photon and proton beams, before treatment planning and treatment facility design can be further developed. The focus of my research was to investigate dosimetric properties of VHEE beams, highlight areas in which there are potential advantages and also to explore potential limitations in their use for radiotherapy. Experimental studies were conducted at CLEAR and CLARA user facilities investigating effects of inhomogeneities on VHEE dose profiles. Previously, only limited Monte Carlo studies with air cavity effects on VHEE and photon dose profiles have been published. Simulation studies by C. Desrosiers et al. in 2000 with spherical air geometries in water phantoms suggested that VHEE dose profiles are less sensitive to low-density regions within the target volume compared to photon beams.