The constriction of Maxilla is considered a common disorder in daily clinical practice; which is usually accompanied with narrow nasal cavity. Many techniques are used to expand constricted maxilla; such as slow maxillary expansion and rapid maxillary expansion. The aim of this study is to evaluate changes in nasal cavity width after slow maxillary expansion by using Spring Jet II expander in late mixed dentition; and to compare them with changes caused by rapid maxillary expansion using Hyrax expander .