An assembly machine for producing multicomponent cigarettes, each comprising a number of portions, which have a central axis and comprise at least one portion defined by a filtering element, and at least another portion defined by an aromatic, preferably tobacco-based, element; the assembly machine comprising: a combining unit for forming groups of portions, each comprising at least two different first portions (3A, 3B, 3C) aligned axially and contacting end to end, and in which the groups of portions travel perpendicularly to their central axis; a first wrapping unit (WU 1), which receives a succession of groups of portions from the combining unit, successively feeds the groups of portions parallel to their central axis, and winds a strip of wrapping material about the succession of groups of portions to form at least one continuous rod of portions; the first wrapping unit (WU 1) comprising a cutting device for cyclically and transversely cutting groups of portions in respective tubular wraps off the continuous rod of portions; a second wrapping unit (WU 2), which receives the groups of portions in respective tubular wraps from the first wrapping unit (WU 1), feeds the groups of portions in respective tubular wraps perpendicularly to their central axis, and winds a sheet of wrapping material about each group of portions in a respective tubular wrap; and a first transfer unit (TU 1) interposed between the combining unit and the first wrapping unit (WU 1) such that the combining unit and the first wrapping unit (WU 1) being arranged at a 90° angle; the assembly machine being characterized by comprising a second transfer unit (TU 2) interposed between the first wrapping unit (WU 1) and the second wrapping unit (WU 2) wherein the first wrapping unit (WU 1) and the second wrapping unit (WU 2) are arranged at a 90° angle such that the assembly machine has a U-shaped layout and the combining unit is positioned facing the second wrapping unit (WU 2) and; the assembly machine is characterized in that the second wrapping unit (WU 2) comprises a wrap feed unit for supplying the sheets of wrapping material; and a portion feed unit located upstream from the wrap feed unit to insert second portions into the groups of portions and comprising a hopper containing a mass of second portions; a cutting drum for cutting the second portions transversely to the desired length; and a pickup drum, which withdraws the second portions successively from the hopper and cooperates with the cutting drum. a combining unit for forming groups of portions, each comprising at least two different first portions (3A, 3B, 3C) aligned axially and contacting end to end, and in which the groups of portions travel perpendicularly to their central axis; a first wrapping unit (WU 1), which receives a succession of groups of portions from the combining unit, successively feeds the groups of portions parallel to their central axis, and winds a strip of wrapping material about the succession of groups of portions to form at least one continuous rod of portions; the first wrapping unit (WU 1) comprising a cutting device for cyclically and transversely cutting groups of portions in respective tubular wraps off the continuous rod of portions; a second wrapping unit (WU 2), which receives the groups of portions in respective tubular wraps from the first wrapping unit (WU 1), feeds the groups of portions in respective tubular wraps perpendicularly to their central axis, and winds a sheet of wrapping material about each group of portions in a respective tubular wrap; and a first transfer unit (TU 1) interposed between the combining unit and the first wrapping unit (WU 1) such that the combining unit and the first wrapping unit (WU 1) being arranged at a 90° angle; the assembly machine being characterized by comprising a second transfer unit (TU 2) interposed between the first wrapping unit (WU 1) and the second wrapping unit (WU 2) wherein the first wrapping unit (WU 1) and the second wrapping unit (WU 2) are arranged at a 90° angle such that the assembly machine has a U-shaped layout and the combining unit is positioned facing the second wrapping unit (WU 2) and; the assembly machine is characterized in that the second wrapping unit (WU 2) comprises a wrap feed unit for supplying the sheets of wrapping material; and a portion feed unit located upstream from the wrap feed unit to insert second portions into the groups of portions and comprising a hopper containing a mass of second portions; a cutting drum for cutting the second portions transversely to the desired length; and a pickup drum, which withdraws the second portions successively from the hopper and cooperates with the cutting drum.