Just like any other human activity, using the Internet is subject to assessment in view of people's development. For many years the attempts have been made to determine the reasonable limits of using the Internet. Recently, psychologists began to point at the phenomenon of the addiction to the world wide web. Also, there is an ongoing work on elaborating diagnostic measures of Internet addiction or compulsion of using it. The majority of researchers refer to the criteria of addiction as specified by the DMS-IV or ICD-10 with regard to psychoactive substances. This article presents the outcome of adaptive researches of the Compulsive Internet Use Scale. The tool has been translated and applied upon two groups, of which the first one consisted of adult people (N=53) and the second included elementary school pupils (N=87). In both researches very high Cronbach's alpha coefficient has been obtained, therefore using the aforesaid tool for further researches is justified. In the group of adults no instances of compulsory Internet use were found, whereby in the group of 12-year olds there have been several cases of highly compulsive Internet activity.