A cooling fan comprises a housing (1, 3) and a motor (2, 4). The housing (1, 3) includes a support portion (1a, 3a), a cover portion (1b, 3b) and a lateral wall portion (1c, 3c), with the lateral wall portion (1c, 3c) disposed between the cover portion (1b, 3b) and the support portion (1a, 3a), with the lateral wall portion (1c, 3c), support portion (1a, 3 a) and the cover portion (1b, 3b) defining a compartment (11, 31), and with the lateral wall portion (1c, 3c) having at least one lateral air inlet (12, 32) and at least one lateral air outlet (13, 33) penetrating through the lateral wall portion (1c, 3c) and communicating with the compartment (11, 31). The motor (2, 4) is mounted inside the compartment (11, 31) of the housing (1, 3) and contains a stator (21, 41) and a impeller (22, 42), with the impeller (22, 42) rotatably mounting to the stator (21, 41), and further containing a hub (221, 421) with a top (223, 423) and a plurality of blades (222, 422), with the top (223, 423) facing the cover portion (1b, 3b), with the top (223, 423) and the cover portion (1b, 3b) delimiting a lateral flow path (23, 43) in the compartment (11, 31), and with each blade (222, 422) being contained in the lateral flow path (23, 43).