Objective. To determine by means of a systematized review on the effect and effectiveness of the use of PEG 3350 to 4000 with or without electrolytes in childhood constipation. Method. The most relevant studies published originally in the English language between the years 1996 to 2016, the database Medline were analyzed. In order to select the studies with the highest scientific evidence, only randomized controlled trials (RCTs), identified by previous reviews, that were revised and updated, and systematic reviews with or without meta-analysis were selected. Results. 25 studies were identified; however, only 19 were part of the scope of this review on the use of PEG 3350 to 4000 with or without electrolytes in childhood constipation. The selected studies were judged by an independent reviewer. The use of PEG 3350 was identified in 13 studies and 4000 in five studies. It was also observed that in eight studies PEG with electrolytes were used, and in ten studies without electrolytes. A total of 1265 children of both genders and ages ranging from 6 months to 16 years were studied. As to the delineation of the studies, it was found that most of the studies were ren- dered. There was a more significant success in the PEG group compared to other laxatives. Conclusion. The benefits of using PEG with both 3350 and 4000 molecular weight, with or without electrolytes for the treatment of children with functional constipation, were the first choice because it was administered orally and therefore less invasive.