New inclusion complexes tetra-n-propylammonium fluoride–urea–water (2/7/3), 2(n-C3H7)4N+F−.7(NH2)2CO.3H2O (1), tetra-n-propylammonium chloride–urea (1/2), (n-C3H7)4N+Cl−.2(NH2)2CO (2), tetra-n-propylammonium chloride–urea (1/3), (n-C3H7)4N+Cl−.3(NH2)2CO (3), tetra-n-propylammonium bromide–urea–water (1/3/1), (n-C3H7)4N+Br−.3(NH2)2CO.H2O (4), and tetra-n-propylammonium iodide–urea–water (1/3/1), (n-C3H7)4N+I−.3(NH2)2CO.H2O (5), have been prepared and characterized by X-ray crystallography. Crystal data, Mo Kα radiation: (1), space group P21/c, Z = 4, a = 8.560 (2), b = 16.301 (3), c = 37.004 (7) Å, β = 92.31 (3)°, R F = 0.075 for 3945 observed data; (2), space group P21/n, Z = 4, a = 9.839 (2), b = 15.160 (3), c = 14.583 (3) Å, β = 108.82 (3)°, R F = 0.058 for 1770 observed data; (3), space group P21/c, Z = 4, a = 9.866 (2), b = 16.274 (3), c = 15.277 (3) Å, β = 103.36 (3)°, R F = 0.060 for 2272 observed data; (4), space group P1¯, Z = 2, a = 8.857 (2), b = 10.639 (2), c = 15.115 (3) Å, α = 88.01 (3), β = 75.02 (3), γ = 66.72 (3)°, R F = 0.064 for 2694 observed data; (5), space group P1¯, Z = 2, a = 9.045 (2), b = 10.781 (2), c = 15.169 (3) Å, α = 87.98 (3), β = 76.00 (3), γ = 65.73 (3)°, R F = 0.052 for 4973 observed data. In the crystal structure of (1) an alternate crisscross arrangement of urea ribbons, which are cross-bridged by other urea molecules, water molecules and fluoride ions, generates a three-dimensional host lattice containing an open-channel system running parallel to the b axis, with the (n-C3H7)4N+ cations accommodated in a zigzag column within each channel. In the crystal structure of (2) the cations are sandwiched between puckered layers resulting from parallel urea ribbons that are cross-bridged by chloride anions. In (3) the (n-C3H7)4N+ cations are accommodated in a channel-type host lattice built of planar arrays of twisted ribbons constructed from three independent urea molecules, which are cross-linked by bridging chloride ions. Complexes (4) and (5) are isomorphous with the same channel host framework built of parallel corrugated urea layers that are interlinked by cyclic (H2O.X −)2 tetramers.