In 2006 Maria Lassén-Seger presented her thesis, Adventures into Otherness: Child Metamorphs in Late Twentieth-Century Children’s Literature at the Åbo Akademi University, Finland.
 
She started teaching on the subject of children's literature in 2000, and has trained both teachers and has worked with both teachers and librarians, giving them additional training on the subject. She is a critic of children’s literature at the Finnish newspaper Hufvudstadsbladet and also board member for the Finnish Institute of Children’s Literature. She is an expert associate for the magazine Children’s Literature in Education and member of The International Research Society for Children's Literature (IRSCL).

A former board member of Norchilnet, a Nordic Research Network focusing on children and reading, and participant of the Chilpa-project at Åbo Akademi University, combining theoretical knowledge of children’s literature with practical elements such as teaching, she is the author of both academic papers and pamphlets on reading for an audience of children, schools and libraries.

Maria Lassén-Seger lives in Åbo, Finland, with her photographer husband and a son, with whom she enjoys trading reading tips.