The aim of this research was to identify the motivations for citation to Wikipedia in scientific papers. Also, the number of citation to Wikipedia, location of citation, type of citing papers, subject of citing and cited articles were determined and compared in different subject fields. From all English articles indexed in Scopus in 2007 and 2012 that have cited Wikipedia, 602 articles were selected using stratified random sampling. Content analysis and bibliometric methods were used to carry out the research. Results showed that there are 20 motivations for citing Wikipedia and the most frequent of them are providing general information and definition, facts and figures. Citations to Wikipedia often were in the introduction and introductory sections of papers. Computer sciences, internet and chemistry were the most cited subjects. The use of Wikipedia in articles is increasing both in terms of quantity and diversity. However, there are disciplinary differences both in the amount and the nature of use of Wikipedia.