In eastern Japan, the term 'chirashizushi' tends to mean a type of sushi comprising of vinegared rice topped with sashimi slices, i.e. ingredients for nigirizushi (sushi shaped by hand) which originated in the Edo period, while it generally refers in western Japan to a kind of sushi that is made of vinegared rice either mixed with or topped with finely chopped ingredients of various kinds excluding raw foods.
「ちらし寿司」という名称では、主に東日本では江戸発祥の、握り寿司のネタ用の刺身などを寿司飯の上に並べた寿司と指し、西日本では生物を使わず、様々な具材を細かく切ったものを酢飯に乗せた寿司あるいは混ぜ込んだ寿司を指す傾向がある。