Söderberg is one of the most important translators of Latin American and Spanish authors and poets in Sweden, including Jorge Luis Borges, Federico García Lorca, Octavio Paz, and Blas of Hill. He has published several anthologies of poetry: of Latin-American poets, surrealism, Cuban poets and most recently,a bilingual edition of Chilean poets, selected as the best foreign book in the Fair of the Book of Santiago de Chile in 2003. He has also translated theatre: Lorca and Buero Vallejo among others.

Among his books in spanish: Pájaro en mano, (Barcelona, 1986), Devenir; Flechas contra la luna (Málaga 1990), Ángel Caffarena, translation by René Vázquez Díaz; Nueve damas españolas y un cura desgarrado (Málaga 1997, with illustrations of Antonio Saura). El Caracol de Europa (Bogotá 2003),Simón Editor, translation of Giovanni Rojas and Víctor Rojas; El otro brillo (Córdoba 2004) ediciones Caja Sur, translation in collaboration with Cuban and Spanish poets. The most recent: Las Piedras de Jerusalén (La Habana 2009), Arte y Literatura, translation Lasse Söderberg / Ángela García.

Director of The international days of Poetry in Malmö (1987 - 2006) presenting international authors and introducing new generation of poets.