Background Dermal fillers are used widely; some have a permanent effect, whereas others are temporary. The aim of this study is to describe the ultrasonographic features of permanent and temporary fillers injected into patients for cosmetic purposes. Materials and methods Between December 2006 and April 2009, 36 subjects, aged 25-45, who had received lips or nasolabial fold filler augmentation, were enrolled for a high-frequency sonographic examination by a blinded investigator. The criteria for exclusion were a history of autoimmunity, infection, neoplastic diseases or episodes of local reactions to the injected filler. Twenty patients underwent a sonographic exam after the injection of a temporary filler (collagen or hyaluronic acid) by FRG; the rest were enrolled among patients seeking a consultation for further cosmetic reasons, but had been treated with an identifiable filler before. Results It was always possible to identify the filler at the site of injection. Seldom was it possible to discover a silent inflammatory reaction, otherwise unsuspected. The sonographic images differed according to the temporary or the permanent nature of the filler. Conclusion Ultrasonography has proved to be a useful, non-invasive tool for the identification of the presence and type of the filler injected.