Dillens studied under Eugène Simonis at the Académie Royale des Beaux-Arts.
In 1877 he received the Prix de Rome for A Gaulish Chief taken Prisoner by the Romans.
[1] For the pediment of the orphanage at Uccle, Figure Kneeling (Brussels Gallery), and the statue of the lawyer Hippolyte Metdepenningen in front of the Palais de Justice at Ghent, he was awarded the medal of honor in 1889 at the Paris Universal Exhibition, where, in 1900, his Two Statues of the Anspach Monument gained him a similar distinction.
[1] Additional works produced by Dillens include An Enigma (1876), the bronze busts of Rogier de la Pasture and P. P. Rubens (1879), Etruria (1880), The Painter Leon Frederic (1888), Madame Léon Herbo, Hermes, a scheme of decoration for the ogival façade of the hotel de ville at Ghent (1893), The Genius of the Funeral Monument of the Moselli Family, The Silence of Death (for the entrance of the cemetery of St Gilles), two caryatids for the town hall of St Gilles, presentation plaquette to Dr Heger, medals of MM.
Godefroid and Vanderkindere and of The Three Burgomasters of Brussels, and the ivories Allegretto, Minerva and the Jamaer Memorial.