Chronic constipation is a common functional disorder of the gastrointestinal tract, affecting up to 35% of the general population, and especially the elderly. However, its definition as perceived by the patient can vary, making it difficult to understand the problem and find appropriate therapeutic measures. The approach to chronic constipation, thus, needs a thorough understanding of the patient's complaint and the main pathophysiological mechanism requiring treatment. Lifestyle changes do not usually meet with complete patient satisfaction. Other treatments include different types of laxatives. Of these, osmotic laxatives appear one of the most effective and are, therefore, frequently prescribed. This review will cover the topic of osmotic laxatives, specifically focusing on polyethylene glycol (PEG/macrogol 4000) in chronic constipation and as a key agent for bowel cleansing prior to colonoscopy. PEG formulations, including macrogol 4000, are safe, effective treatments for constipation, even in children and elderly patients. Macrogol 4000 may well be more palatable than combined formulations (macrogol 3350 with electrolytes), which could help improve adherence to the long-term treatment required for chronic constipation. PEG/macrogol is also recommended as an effective option for bowel cleansing prior to colonoscopy. The improved cost-effectiveness of macrogol over other commonly prescribed laxatives, such as lactulose, should be taken into consideration.