He attended a local elementary school called Kungsholms Folkskola, which, at the beginning of the twentieth century, was the world"s largest elementary school - the school had a capacity of 3,800 pupils, but since not all of them attended school every day, they were taught in shifts and according to the City Museum of Stockholm, the total number of enrolled pupils was over 6,000.
Forssell was a versatile writer who worked within many genres, including poetry, drama and songwriting. He studied in the United States during the 1940s, returned to Sweden to study for a degree at the University of Uppsala in 1952 and became a cultural reporter for various Swedish newspapers and journals (Utsikt, Bonniers Litterära Magasin, Poesi, Dagens Nyheter and Expressen). At the same time, he became established as a lyricist for cabaret shows and his own reviews (including Två åsnor (A Pair of Donkeys) which was staged in Gothenburg in 1957).
During the 1970s he worked tirelessly as a poet and as a song-contest lyricist, including writing for the 1973 Swedish Eurovision Song Contest entry selection round (Melodifestivalen) and for performer Lill-Babs in 1980.
Lars Forssell died in Stockholm in 2007.
In 1966 he was a member of the jury at the 16th Berlin International Film Festival.