The present invention is related to cooking oven (1) for foodstuffs comprising: - a cooking chamber (2), wherein foodstuffs can be placed for being cooked, - a vapour outlet duct (9) configured for discharging vapour from the cooking chamber (2) to the external of the cooking oven (1), - a cleaning system (70) for cleaning the cooking oven (1), comprising a vapour outlet duct cleaning pipe (450) configured for taking a cleaning liquid within said vapour outlet duct (9). The vapour outlet duct (9) comprises an internal surface (90) having a circular, or substantially circular, or oval, or substantially oval, cross section. The vapour outlet duct cleaning pipe (450) is configured for emitting within the vapour outlet duct (9) a flow of cleaning liquid (451) generating a swirl of cleaning liquid (452) flowing on the internal surface (90).