Semipolar GaN-based light emitting devices show great promise because of reduced polarization-related electric fields in the quantum wells and the potential for high indium uptake in InxGa1-xN quantum wells. In semipolar GaN, the (0001) slip plane is inclined with respect to the film normal, thus shear stresses are present on this plane for nominally misfitting layer growth. We present scattering contrast transmission electron microscopy studies of (1122) and (2021) semipolar GaN-based laser diode structures. Misfit dislocations were observed at the nominally misfitting heterointerfaces in the (1122) structures with line direction  and Burgers vector in the (0001) plane. Similar observations are reported for the (2021) structures. Overall, the results are consistent with stress relaxation by threading dislocation glide.