The scope of the work involves analysis of the possibilities regarding radiometric adjustment of orthoimages based on the LAB colour model instead of the RGB model. The first part emphasises relevance of the radiometric adjustment problem in the context of performing photogrammetric projects on the basis of a few hundred or even thousands of photographs. Then, the LAB colour space is presented compared to other models. The next chapter contains comparison between the LAB model and the RGB model, indicating advantages of the former one. Since the theoretical discussion allowed to draw a conclusion about advantages of applying the LAB model in radiometric adjustment of orthoimages, the next part presents formulated outline of a concept for orthoimage mosaic on the basis of the LAB model. Then, a research experiment is discussed, in which researchers have used orthoimages derived from two different photogrammetric projects. An analogue camera was applied in one of them, and digital camera in the other. Orthoimages are characterised by very strong radiometry diversification. Warm tones with excessive yellow prevail in one orthoimage, while the other one has cold tonality, containing too much ashen green. Another difference is the degree of interference content in one it is high and in the other low. Such radiometry diversification constitutes a considerable problem during mosaicing. Orthoimages went through mosaicing in the RGB model and in the LAB model separately. In neither of the cases full tonal uniformity was obtained, but image edited in the LAB model is much better. The experiment results are deemed to confirm the LAB space usability for radiometric adjustment of orthoimages.