The purpose of the study is to analyze the PIRLS 2006 items to check if a differential item functioning (DIF) can be noticed. The national data are analyzed and the groups of comparison are based on gender since PIRLS 2006 study showed that Latvia has the 6th largest gender gap in reading literacy scores. The DIF analysis is expected to show whether the measurement instrument could be one of the reasons of the gender gap in achievement. The results show that the set of PIRLS 2006 items does not have any gender bias on Latvian students since there are items with no DIF at all, whilst there is an almost equal number of items with DIF in favor of each of the sexes. The length of the item stem does not have any correlation with the item difficulty or differential item functioning between sexes. There is no difference in DIF when the items of literary and informative texts are compared - this is also true for multiple choice and constructed response items. The main conclusion is that the gender achievement gap in Latvia is caused by the differences in their skills/abilities and not by a differential item functioning.