UGS have been positively associated with stress-related illnesses. Paradoxically the densification tendency in western cities causes decreasing access to green environments. City planners and landscape architects are challenged when designing such areas due to a lack of space and knowledge about which environmental characteristics users prefer in relation to mental restoration. We investigate nine small public urban green spaces (SPUGS) in the dense city of Copenhagen in order to determine which environmental characteristics may influence the perceived restorativeness of SPUGS amongst average users and the most stressed users. We conducted an on-site questionnaire survey where respondents answered the perceived restorativeness scale (PRS), which is based on the ART theory, and a question regarding their preferences. All SPUGS were expertly evaluated using the eight perceived sensory dimensions (PSDs). First, seven of the eight PSDs could be used in the study and positive significant relations were found between the PDSs and the users’ perceived restorativeness. Second, the PSDs ‘social’ and ‘serene’ significantly influenced both average users and the most stressed users’ perceived restorativeness. And third, ‘nature’ was significantly correlated with the most stressed users’ perceived restorativeness. The preference for the PSDs in relation to mental restoration differs between SPUGS and larger urban green environments. The results indicate that the PSDs can be useful for the future design of SPUGS with the potential for mental restoration. However, further development is necessary to make the PSDs´ more user friendly.