Excimer laser radiation (XeCl, lambda=308 nm and ArF, lambda=193 nm) has been used both to cut chemical vapour-deposited diamond-coated tungsten wires (diamond fibres) of diameter less than or equal to 200 mu m and to smooth and profile the diamond surface. The effects of ablation and localized heating in the focal volume on the diamond and the tungsten core are described, and compared with results obtained for a Nd:YAG laser. The laser fluence and/or intensity, beam homogeneity and angle of incidence were identified as key parameters in ultraviolet laser-induced ablation of diamond-coated wires and fibres. Surface smoothing may lead to increase fibre strength.