Public greenery represents a very important type of environment in any town. Its positive linkage to the quality of life of urban population has been frequently discussed in pertinent professional literature while negative aspects remain poorly described, with only one exception – its association with danger of crime and vandalism. However, use of public urban greenery can be also problematic due to another kind of problems. It occasionally can serve as a habitat for particular plant and animal species that can make visitors stay there very unpleasant and uncomfortable. Identification of the level of information of urban inhabitants on particular dangerous organisms was one of principal questions addressed within the project named "Organisms endangering greenery users in urban environment – consequences for planning and management". The article is intended to report on selected outputs of sociological questionnaire survey conducted within the project.