Analysis of the European context has made it possible to enrich our knowledge about Tsarevich Peter Petrovich's miniature portrait created by Johann Gottfried Tannauer inside a snuff-box with a view of St Petersburg on the outside, from the State Hermitage Museum collection. The paper identifies the source of iconography of the child in this portrait, which has so far been considered to be an original creation of the artist. It is one of the engravings portraying Prince William, Duke of Gloucester after Sir Godfrey Kneller's painting (ca. 1691, The Royal Collection Trust, Hillsborough Castle). The Duke's portrait was often used as a source of iconography for children's portraits in Europe. The headwear with two ostrich feathers which was a traditional marker of nobility and, most importantly, in some cases – an attribute of the heir of the title, is likely to have been borrowed from another source – a portrait of Charles Fitzroy, 2nd Duke of Grafton, also based on Sir Godfrey Kneller's painting. Although the authors of numerous children's portraits (fifteen paintings) based on the portrait of Prince William made use of the same source, they managed to create various images corresponding to the characteristics of young models and the circumstances of commission. Whereas William of Gloucester is depicted against the background of a landscape with an arcade, behind Tsarevich Peter is some water space with ships and a fragment of a fortress wall obviously symbolizing the new capital of Peter the Great. The headdress and the presence of an oval portrait of Peter I in the composition proves that Peter Petrovich was his father's hope and the new heir to the Russian throne: his status was confirmed in the Manifesto of 3 (14) February 1718.