Besides the church, Diegem had several small chapels. In 1900 parish priest Meeus listed six: Our Lady of Lourdes, Our Lady of the Rosary, Saint Roch, Saint Cornelius and two more chapels of Our Lady, one of which, the ‘Koben Ommes kapelleke’, was much visited by people suffering from fever. The sisters' convent also had its own chapel.
The Saint Roch chapel
When contagious diseases broke out again around the middle of the 19th century, parish priest Veulemans obtained for the church a relic of Saint Roch, patron saint against the plague. On 20 September 1849 his statue was carried in procession to a new chapel in the Molenstraat, built by the widow Joanna Poot-Van Pevenage. In 1851 she gave the chapel, with a metre of ground around it, to the church. The chapel was demolished in 1976.
Lourdes and Prague
In 1912 a chapel to the Infant Jesus of Prague was built at Broekstraat 52. The chapel of Our Lady of Lourdes was made of rough stone from the sand pits; it disappeared in the 1930s when the Woluwe was covered over, but in 1931 it was rebuilt in a new form across the Haachtsesteenweg, against the sisters' school.