Léon de Smet studied, as did his brother Gustaaf, at the Academie voor Schone Kunsten in Ghent, where his mentor was Jean Joseph Delvin. Although he lived in Laethem-St-Martin between 1906 and 1913, he was not a member of the Laethem Expressionist group, being primarily influenced by Impressionism. He became a member of the Luminist Life and Light ( Vie et Lumière) Group alongside Theo van Rysselberghe. In 1914, while his brother Gustaaf was in self-imposed exile in the Netherlands after the outbreak of World War I, Léon de Smet moved to Germany. He returned to Brussels after the war and finally settled in Deurle in 1926.

Spending some time in England, de Smet painted chiefly portraits of authors, including those of John Galsworthy, George Bernard Shaw and Joseph Conrad, as well as portraits of London society figures. Immediately after the war, he flirted briefly with Expressionism but soon reverted to his Impressionist style with which, unlike his Expressionist counterparts, he celebrated predominantly 'happy moments', as exemplified by his Bath-time and Harmony in White (1909), Interior (1912), Deurle in the Snow (1938) and Intimacy (1941).

De Smet's work featured at the 1909 Venice Biennale, and he also exhibited at the Leicester Galleries in London. Following his death, his work was shown at the De Vuyst gallery in Lokeren, most notably in 2003.

Museum and Gallery Holdings

Antwerp (Mus. Flamand): Portrait of Herman Teirlinck; Portrait of Auguste Vermeylen; Portrait of Styn Streuvels
Brussels (Mus. royaux)
Deurle (Mus. Leon De Smet)
Ixelles (MBA)