Dislocations are common defects in both natural as well as in CVD-grown diamond. Recent advances in the growth of high quality single crystal CVD diamond have led to an increased interest in the atomistic and electronic structure of ‹100› dislocations. These dislocations are observed as mixed-type 45° and pure edge dislocations. Hence in this work we present ab initio modelling studies on these two types of dislocations. The 45° dislocation is found to be by far more stable than the pure edge and both dislocations lead to states in the electronic band gap. An alternative structure for the mixed-type dislocation, which is not straight but kinked and consists of short edge and screw segments, was found slightly higher in energy than the straight structure.