Diffusion-induced dislocation loops in GaP and GaAs were analysed by means of large-angle convergent beam electron diffraction (LACBED) and conventional contrast methods of transmission electron microscopy. It is demonstrated that LACBED is perfectly suited for use in analysing dislocation loops. The method combines analyses of the dislocation-induced splitting of Bragg lines in a LACBED pattern for the determination of the Burgers vector with analyses of the loop contrast behaviour in transmission electron microscopy bright-field images during tilt experiments, from which the habit plane of the dislocation loop is determined. Perfect dislocation loops formed by condensation of interstitial atoms or vacancies were found, depending on the diffusion conditions. The loops possess {110}-habit planes and Burgers vectors parallel to ⟨110⟩. The LACBED method findings are compared with results of contrast analyses based on the so-called inside–outside contrast of dislocation loops. Advantages of the LACBED method consist in the possibility of determining the complete Burgers vector of the dislocation loops and of an unambiguous and fast loop type analysis.