Background: The guidelines for treatment of CAP and Ventilator-Associated pneumonia (VAP) have largely been based on empirical date, and are not evidence based. Shortening the usage of antibiotics can reduce the emergence of antibiotic resistance, cost and side-effects, and improve compliance and tolerance. Objective: To see if any evidence-based conclusion can be drawn concerning the length of treatment of CAP and VAP. Methods: A Literary Review: A search in the Cochrane Library was made for typical and atypical CAP, as well as for VAP. Three meta-analysis, one literary review and 32 RCTs were included. Results: There are indications that mild-to-moderate CAP in adults can be successfully treated with azithromycin by a single dose of 2.0 grams, or with ≤ 7 days of gemifloxacin, amoxicillin, telithromycin, ceftriaxone and cefuroxime. A three-day treatment with primarily amoxicillin for children between 2-59 months, and four days of ampicillin and gentamicin for neonates, was found to be both efficient and safe. Atypical CAP has successfully been treated with azithromycin for three days in grown-ups, and possibly five in children. VAP can possibly be treated for seven-to-eight days. Conclusion: Studies found a more or equally as favourable tendency overall towards short treatment, especially with the usage of azithromycin, in terms of safety and efficacy. More studies are needed to draw evidence based conclusions that can be translated into guidelines.