At present 75 % of Europeans live in urban settlements. This percentage is expected to increase up to 80 % by 2020. In this context the importance of urban public spaces is increasing. These spaces directly affects the way how local inhabitants perceive the environment in which they live and how this environment fulfils its social and societal functions. The urban public spaces can considerably affect the economic development and prosperity of cities. Their importance also growth in connection to some challenges which have to be addressed at present, though their impacts will be visible in the next decades. First of all, there are threatening adverse impacts of climate change which are more serious in cities than in surrounding landscape. The thesis deals with legislative and development documents, institutional framework, stakeholders and division of responsibilities at the national, regional and local levels in relation to public urban spaces. It specifically focuses on environmental functions of public urban spaces which directly affect the quality of the environment in cities. This includes the issue of climate change, possibilities to assess vulnerability of public urban spaces. Theoretical knowledge has been applied in the thesis in assessment of vulnerability of inhabitants in the city part Bratislava -- Staré Mesto in relation to summer heats from the point of view of quantity and environmental quality of public urban spaces. Based on the results, there are adaptation measures proposed in the final part. The potential how to use the thesis in practice is great. The list of proposed environmental criteria to be applied to public urban spaces should set a framework for application of the thesis in practice. The proposed measures can be in practice implemented at the local level or at the level of the entire city. The thesis, knowledge and results achieved will be used in a number of important documents, e.g. in preparing a chapter on spatial planning in relation to climate change within the National Strategy on adaptation to climate change or in elaborating a chapter on functional component "green areas" in updated "Principles and rules of spatial planning", currently under preparation. Urban planning, as a science area and also a practical activity, should be determined by progressive knowledge of social and nature sciences. In the thesis we have concentrated on some new challenges which will have to be addressed in this area of science in dealing with issues of environmental protection and management and in practical spatial planning activities. Especially, the issue of climate change should be included as a binding indicator for dimensioning all subsystems of a spatial plan, such as transport, energy, water, and in drafting functional regulation (permitted and restricted function) and in the spatial regulation.