The geometric structure, the proton isotropic hyperfine coupling constants and temperature dependence of the isotropic hyperfine coupling constants have been investigated for the silacyclobutane radical cation using Moller-Plesset perturbation theory to second order, the coupled cluster approximation and density functional theory, The temperature dependence of the hyperfine coupling constants is explained employing a one-dimensional model for the description of the ring puckering motion. For the geometrical structure the study supports conclusions made in earlier work based on the measurements of the temperature dependence of the electron spin resonance (ESR) spectra, e.g. the silacyclobutane radical cation possesses an asymmetrically distorted C-1 structure in which one of the Si-C bonds is considerably elongated, and the ring is puckered. A reassignment of part of the ESR spectrum is obtained on the basis of the theoretical results in combination with experimental measurements of the low temperature dynamical behaviour.