The main aim of this study is to evaluate the Internet Use Disorder Scale administered to the sample of Internet users in Serbia, as well as to confirm its factorial structure and correlate it with some parameters of Internet use. The total sample included 280 participants, divided into the clinical (70) and control group (210), age (M=26.73, SD=7.830). The control group was randomly formed out of the total number of the participants (327) who voluntarily responded to the test battery and fulfilled the entry criteria. The clinical group comprised the subjects who had sought professional help due to the symptoms of dysfunctional Internet use in some of the institutions or private psychiatric and psycho-therapeutic practices in Serbia, all of whom met the classification criteria of Internet use disorder. The internal consistency of the scale is α=.944, and through factor analysis three factors were extracted, together explaining 67.23% of the total variance: Inability to control behaviour and the consequences, Internet preoccupation and responses to deprivation, Social consequences of Internet use disorder. A statistically significant difference between the total scores of the clinical and control group on the scale was reported (t(278)=20.434; p<.000), and all individual items showed significant discriminative values with 89.6% of the participants regularly classified into appropriate categories. In addition, a significant positive correlation between the PUI score and the amount of hours spent online was found (r=.524; p<.001), however the analysis did not show any correlation with the work experience and age variables, nor significant differences by the sex, education and place of residence criterion in the clinical group. These results are similar to the ones with the control group accept for a low correlation between the PUI score and age (r=-0.253; p=.001).