The descriptive statistics in one hand, and the analytic statistics by using “F” test on the other revealed the following results:  the performance of students at An-Najah National University (x=3.01) was significantly (α = .000) affected negatively by using (SMN) more than their counterparts at Al-Quds Open University (x=2.66).  This negative effect appeared significantly between the two universities on social and health domains but not on the academic one, though the mean on this domain was relatively high at both universities.  It placed in the second rank for An-Najah students and in the first one for Al-Quds Open students.  F-test on the other hand didn’t show a significant main effect between males and females, but it did show such significants on the other variables.  These significant effects were summarized as follows:  the students of other colleges such as commercial and social, were affected negatively more than the students of  humanities and scientific colleges; freshmen and senior students were more affected than the sophomore or junior students; students whose specializations’ stream at high school in commercial or industrial were affected more than those whose specializations were in literature or science; students who have a weak grade points average at university were affected more than those who have good, very good, or excellent grades; students who spend seven hours daily or more on (SMN) were affected more than those who spend less than seven hours; students who work during their studies were affected more than those who don’t work;  and students who don't have a hobby in their life were affected more than those who do have a hobby.

Accordingly, the researcher recommended the people who are in charge at universities conduct seminars on the usages of (SMN) and its possible negative effects on students’ performances in order to guide them to use it properly.