Shrouds and substrate treating systems including the same are provided. Substrate treating systems may include a process chamber, a supporter, and a plasma source that is spaced apart from the supporter in a vertical direction. The substrate treating systems may also include a shroud configured to contain the plasma therein. The shroud may include a sidewall portion and a first flange portion extending horizontally from the sidewall portion and including a plurality of first slits that extend through a thickness of the first flange portion. The first flange portion may define a first opening, and a portion of the supporter may extend through the first opening. The sidewall portion may include a plurality of second slits, and each of the plurality of second slits may extend through a thickness of the sidewall portion and may extend from one of the plurality of first slits toward the plasma source.