The fall of the socialist system in the late 1980s determined major changes in the economy of former socialist countries. These changes affected especially the mono industrial cities. Even after privatisation, the industrial sector remained in restructuring and decline, often leading to the closure of factories. Structural or functional conversion processes have been delayed and on the site of former factories remain many abandoned places, which were neglected by the authorities. These areas influence both the natural and socio-economic environment: from local community to potential investors. Since the brownfield areas were not given much attention, this paper contributes to a correct definition, identification and presentation of such sites and the main barriers that hinder their redevelopment. For the case study, two mono industrial cities from two neighbouring former socialist countries (Romania and Serbia) were analysed. The object of the study was the comparison of the redevelopment solutions applied so far with their impact on socio-economic environment and the plans for future development.