In the context of the research project ’The Quality of Life in Small and Medium-sized Cities’ sponsored by the German Ministry of Education and Research (2002-2005) the network of seven Cities in Brandenburg (Germany) has developed an monitoring system regarding the quality of life. An essential aim was the assessment of objective living conditions and subjective well-being. An objective data-set expanded by a survey about subjective well-being of the citizens. Because the monitoring system should be operated by the cities themselves after the funding for the project has run out, an online questionnaire should deliver the level of satisfaction enjoyed by the city population. A main target was to test the suitability of this instrument especially in small and medium-sized cities. Therefore the number of completed questionnaires, the extent of selection of the answering group as well as the quality of the answers were tested by a parallel conducted telephone survey. In the two years the participation was very stable (2003: 1.324; 2004: 1291), although levels of participation in one city varied from year to year. The opinions of residents were very similar concerning the results of the telephone- and the online-based survey. The differences lay in more critical replies corresponding to the social structure of the participants. The online users tend to be younger, better educated and employed. Furthermore, more men took part in the onlinebased questionnaire. Fundamentally, online-based questioning is a suitable method for collecting subjective data especially in medium-sized cities. In small towns there is a problem of inadequate participation. The instrument is useful for showing trends, but not for conducting a representative study.