A South Portland agency that addresses youth substance abuse and mental health has hired a new CEO.

Gregory Bowers has been selected to assume leadership of Day One by its board of directors, according to a release from the agency. Bowers had been the interim CEO of Community Partners in Biddeford, and was the executive vice president and chief operating officer at Maine Behavioral Healthcare, where he worked for 18 years.

Dennis Carrillo, president of the board, and head of the CEO search committee, cited Bowers’ strong history of nonprofit leadership in Maine and his wealth of experience as reasons for the selection.

Noting the substance abuse crisis affecting Maine and the nation, Bowers said Day One’s history of providing exceptional service is part of what drew him to the job.

“Now more than ever, this agency’s mission is proving to be critical in our state’s response to these significant challenges,” he said in the release. ” I am proud to be joining this tremendously talented and committed staff in continuing to grow and expand the significant impact Day One has on our communities.”

Day One was founded in 1973, with a single residential treatment facility and has expanded to include two residential treatment facilities for boys and one for girls; individual and group outpatient counseling; programs for homeless youth; case management; school-based counseling; services for youth and adults at two corrections centers; and the Natural Helpers peer-to-peer prevention program for high school students.