Let Γ ⊂ PSL(2, R) be a discrete and finite covolume subgroup. We suppose that the modular curve Γ\H is "embedded" in a Hilbert modular surface Γ K \H 2 , where Γ K is the Hilbert modular group associated to a real quadratic field K. We define a sequence of restrictions (ρn) n∈N of Hilbert modular forms for Γ K to modular forms for Γ. We denote by M k 1 ,k 2 (Γ K ) the space of Hilbert modular forms of weight (k 1 , k 2 ) for Γ K . We prove that P n∈N P k 1 ,k 2 ∈N ρn(M k 1 ,k 2 (Γ K )) is a subalgebra closed under Rankin-Cohen brackets of the algebra L k∈N M k (Γ) of modular forms for Γ.