Device for purifying vehicle exhaust gases, the device comprising: - a first purification member comprising a first substrate for purifying exhaust gases, the exhaust gases circulating in the first substrate according to a first direction, the first substrate having, perpendicular to the first direction, a first section having a first perimeter; - a second purification member comprising a second substrate for purifying exhaust gases, the exhaust gases circulating in the second substrate according to a second direction substantially opposite to the first direction, the second substrate having, perpendicular to the second direction, a second section having a second perimeter; - the first and second purification members (20, 24) being disposed side by side and substantially parallel one to the other, such that the respective first and second surfaces (42, 44) of the first and second substrates (22, 26) are placed opposite each other; - the first surface having, perpendicular to the first direction, a first width greater than 7% of the first perimeter, the second surface having, perpendicular to the second direction, a second width greater than 7% of the second perimeter, the first and second surfaces (42, 44) having respective shapes co-adapted such that at least one of the first and second surfaces (42, 44) is separated at every point from the other of the first and second surfaces (42, 44) by a distance less than 30 mm, preferably less than 25 mm, characterised in that: - the first purification member comprises a first external envelope having a first peripheral wall which, regarded perpendicularly to the first direction, surrounds the first substrate entirely; - the second purification member comprises a second external envelope having a second peripheral wall which, regarded perpendicularly to the second direction, surrounds the second substrate entirely; - the first and second peripheral walls (46, 48) being separate one from the other. - a first purification member comprising a first substrate for purifying exhaust gases, the exhaust gases circulating in the first substrate according to a first direction, the first substrate having, perpendicular to the first direction, a first section having a first perimeter; - a second purification member comprising a second substrate for purifying exhaust gases, the exhaust gases circulating in the second substrate according to a second direction substantially opposite to the first direction, the second substrate having, perpendicular to the second direction, a second section having a second perimeter; - the first and second purification members (20, 24) being disposed side by side and substantially parallel one to the other, such that the respective first and second surfaces (42, 44) of the first and second substrates (22, 26) are placed opposite each other; - the first surface having, perpendicular to the first direction, a first width greater than 7% of the first perimeter, the second surface having, perpendicular to the second direction, a second width greater than 7% of the second perimeter, the first and second surfaces (42, 44) having respective shapes co-adapted such that at least one of the first and second surfaces (42, 44) is separated at every point from the other of the first and second surfaces (42, 44) by a distance less than 30 mm, preferably less than 25 mm, - the first purification member comprises a first external envelope having a first peripheral wall which, regarded perpendicularly to the first direction, surrounds the first substrate entirely; - the second purification member comprises a second external envelope having a second peripheral wall which, regarded perpendicularly to the second direction, surrounds the second substrate entirely; - the first and second peripheral walls (46, 48) being separate one from the other.