A unit for deaeration of drainage water from a paper machine, said unit comprising: - an inlet for receiving the drainage water flowing in a first flow direction; - an outlet for removing the drainage water to a subsequent deaeration channel after the outlet and which outlet forms the outlet of the deareation unit; and - a first chamber that is arranged downstream of the inlet, said first chamber comprising a first chamber part, and a second chamber part that is arranged downstream of the first chamber part, the first chamber part comprising: - a guide wall portion for redirecting the drainage water in a predetermined second flow direction that differs from the first flow direction, said guide wall portion being formed by a plurality of curved guide walls (10, 23) which define a plurality of curved and substantially parallel flow channels for the drainage water and that the guide walls (10, 23) are arranged to interact with the drainage water in such a way that air is forced out of the drainage water, characterized in that the unit further comprises two substantially planar end walls (25, 26), which are substantially parallel to the first flow direction and which are arranged on respective sides of and substantially orthogonally to the guide walls (10, 23), wherein for at least one of the flow channels each end wall (25, 26) exhibits an opening that communicates with the flow channel for removing at least part of the air, which has been released from the drainage water in the flow channel by said interaction, from the first chamber part, and in that the unit comprises a second chamber that is arranged downstream of the first chamber, said openings of the first chamber opening into said second chamber, and in that the first chamber opens into the second chamber through a first pressure drop screen. - an inlet for receiving the drainage water flowing in a first flow direction; - an outlet for removing the drainage water to a subsequent deaeration channel after the outlet and which outlet forms the outlet of the deareation unit; and - a first chamber that is arranged downstream of the inlet, said first chamber comprising a first chamber part, and a second chamber part that is arranged downstream of the first chamber part, the first chamber part comprising: - a guide wall portion for redirecting the drainage water in a predetermined second flow direction that differs from the first flow direction, said guide wall portion being formed by a plurality of curved guide walls (10, 23) which define a plurality of curved and substantially parallel flow channels for the drainage water and that the guide walls (10, 23) are arranged to interact with the drainage water in such a way that air is forced out of the drainage water, characterized in that the unit further comprises two substantially planar end walls (25, 26), which are substantially parallel to the first flow direction and which are arranged on respective sides of and substantially orthogonally to the guide walls (10, 23), wherein for at least one of the flow channels each end wall (25, 26) exhibits an opening that communicates with the flow channel for removing at least part of the air, which has been released from the drainage water in the flow channel by said interaction, from the first chamber part, and in that the unit comprises a second chamber that is arranged downstream of the first chamber, said openings of the first chamber opening into said second chamber, and in that the first chamber opens into the second chamber through a first pressure drop screen.