Mobility of pigment-protein complexes (phycobilizomes and photosystem II playing a key role in photosynthesis) was studied by FRAP method (Fluorescence Recovery After Photobleaching). FRAP represents a fluorescence based microscopy method enabling measurement of protein mobility in living systems. The protein complexes are bleached by a laser pulse. And mobility of unbleached proteins is measured as a fluorescence recovery in the bleached area. Currently we have only limited knowledge about the mobility of photosynthetic proteins. This work was aimed at optimization of the photosynthetic protein mobility measurement by FRAP. I have performed several methodological experiments which led to the successful assessment of phycobilisome and chlorophyll-containing proteins diffusion coefficients in selected red algae (Porfyridium cruentum, Cyanidium caldarium) and cyanobacteria (Synechocystis PCC6803, Acaryochloris marina). The methodology developed and validated in my thesis was then applied in further research projects.