Bush, 88, was in stable condition the day after she entered Methodist Hospital for treatment, KPRC-TV, Houston, reported.
"Former first lady Barbara Bush was admitted to Methodist Hospital in Houston's Texas Medical Center yesterday for treatment on a respiratory related issue," the office of former President George H.W. Bush said in a statement.
"She is in great spirits, has already received visits from her husband and family, and is receiving fantastic care. Updates will be issued when warranted."