The aim of the doctoral thesis was to study the mechanisms of the maintenance of individual features and integrated information in visual-spatial working memory. We designed a working memory model based on the assumption that two systems are involved in the maintenance of information in visual-spatial working memory, i.e. a hemisphere-specific representational system that enables the formation of the representations of relevant information, and an active maintenance system that enables active maintenance of the established representations. Based on the model, we formulated three research questions, which we addressed in three separate studies. In the first we examined whether the capacity of visual working memory is limited both by the representational and active maintenance systems. In the second, we explored whether independent representational and/or active maintenance systems support maintenance of colors and shapes in the visual working memory. In the third, we studied the mechanisms for maintenance of integrated visual and spatial representations. The results of the first study showed that the capacity for maintaining objects’ orientations is limited by the capacity of the representational subsystems of both hemispheres, as well as the capacity of the active maintenance system, and that the capacities of the two systems change very similarly throughout the lifespan. In the second study, we replicated the findings of the first study for maintenance of colors and shapes, and found that the working memory for colors and shapes has a common representational system and independent active maintenance systems. The results of the third study revealed that the integration of color and position is not based on an additional, integration-specific system, but rather on the coordinated operation of a widespread network of brain regions, including regions that preferentially respond to colors and positions as well as other modality non-specific regions. The obtained results address important theoretical issues related to the mechanisms of information maintenance in visual-spatial working memory and the role of representational and active maintenance subsystems, and reveal the complex functioning of the visual-spatial working memory system.