This presentation wants to provide knowledge on mathematics lessons in Japanese classrooms (in comparison to Swedish classrooms). We will focus on a description of arithmetic lessons in the early school years. During a study visit in Sendai and Tokyo in February 2014 we had the possibility to visit lessons in four different elementary schools and to observe teachers’ and pupils’ activities during the mathematic lessons. The ”Japanese way” of organizing mathematics teaching has been described frequently and is being characterised as organising the whole lesson around a small number of problems and with a focus on pupils learning strategies (Shimizu, 2013). In this paper we choose Shimizu and others’ analyses as a starting point and will exemplify how a problem solving perspective can guide the activities of teachers and pupils. We are especially interested in how problem solving can contribute to pupils’ understanding of mathematical terms and content in elementary school lessons early years, when addition and subtraction and related procedures are being taught.