A fan coil unit comprising at least one lower compartment (D, E, F), in fluid connection with the outside, wherein said at least one lower compartment is delimited by respective walls (27, 29, 24) including a first wall substantially parallel to a longitudinal axis and a second wall, opposite the first wall, at least one upper compartment, arranged above said at least one lower compartment (D, E, F), relative to said longitudinal axis, and in fluid communication with it, said at least one upper compartment being delimited by respective walls (28, 25, 240) including two side walls comprising respective side openings, air flow generating means arranged in said at least one lower compartment (D, E, F); and at least one heat exchange portion (32b, 32c; 32d, 32e; 32a) arranged inside said at least one lower compartment (D, E, F) for heating or cooling an air flow generated by said air flow generating means by heat exchange with a heat transfer fluid, wherein said upper compartment comprises a flow diverting channel for diverting said heated/cooled air flow exiting from said at least one heat exchange portion (32b, 32c; 32d, 32e; 32a) towards said side openings; said fan coil unit being characterised in that it comprises a central compartment, a first side compartment adjacent to said central compartment, and a second side compartment, adjacent to said central compartment and opposite said first side compartment, wherein said first side compartment and said second side compartment are arranged below said upper compartment and are divided by respective internal side walls from said central compartment and wherein said at least one heat exchange portion (32b, 32c; 32d, 32e; 32a) is arranged in said central compartment. at least one lower compartment (D, E, F), in fluid connection with the outside, wherein said at least one lower compartment is delimited by respective walls (27, 29, 24) including a first wall substantially parallel to a longitudinal axis and a second wall, opposite the first wall, at least one upper compartment, arranged above said at least one lower compartment (D, E, F), relative to said longitudinal axis, and in fluid communication with it, said at least one upper compartment being delimited by respective walls (28, 25, 240) including two side walls comprising respective side openings, air flow generating means arranged in said at least one lower compartment (D, E, F); and at least one heat exchange portion (32b, 32c; 32d, 32e; 32a) arranged inside said at least one lower compartment (D, E, F) for heating or cooling an air flow generated by said air flow generating means by heat exchange with a heat transfer fluid, wherein said upper compartment comprises a flow diverting channel for diverting said heated/cooled air flow exiting from said at least one heat exchange portion (32b, 32c; 32d, 32e; 32a) towards said side openings; said fan coil unit being characterised in that it comprises a central compartment, a first side compartment adjacent to said central compartment, and a second side compartment, adjacent to said central compartment and opposite said first side compartment, wherein said first side compartment and said second side compartment are arranged below said upper compartment and are divided by respective internal side walls from said central compartment and wherein said at least one heat exchange portion (32b, 32c; 32d, 32e; 32a) is arranged in said central compartment.