A delivery assembly for a machine for preparing liquids product by means of cartridges which have a substantially cup-shaped body that houses an amount of at least one substance capable of forming a liquid product through water and/or steam, the delivery assembly having a substantially horizontal axis and including - an inlet passage, to enable a cartridge to be inserted in the delivery assembly, - an injector device, to let water and/or steam under pressure in the cartridge, - an infusion chamber, facing the injector device and capable of receiving one said cartridge, - retention means (42, 47), capable of maintaining the cartridge in a position substantially coaxial to the infusion chamber and the injector device, - an actuation system, capable of causing relative displacements between the injector device and the infusion chamber, between a spaced position and a close position, the infusion chamber being in a fixed position with respect to a stationary structure of the delivery assembly and the injector device being mounted displaceable with respect to the infusion chamber and the said stationary structure, wherein the retention means (42, 47) are capable of assuming a retention position, in which the cartridge is retained in the said position substantially coaxial to the infusion chamber and the injector device, and a release position, in which the cartridge is free to fall towards an outlet passage of the delivery assembly, wherein the retention means comprise - a support element for supporting the cartridge, the support element being sustained in a displaceable way by the injector device in a part thereof that generally faces towards the outlet passage, the support element being switchable from the said retention position to the said release position in the course of the displacement of the injector device towards the said close position; and - guiding means at generally opposite side parts of the injector device, particularly in substantially diametrically opposite positions, the guiding means frontally protruding from the injector device and being capable of laterally constraining the cartridge and guide it to said position substantially coaxial to the infusion chamber, the delivery assembly being characterized in that the guiding means are in a fixed position at said generally opposite side parts of the injector device. - an inlet passage, to enable a cartridge to be inserted in the delivery assembly, - an injector device, to let water and/or steam under pressure in the cartridge, - an infusion chamber, facing the injector device and capable of receiving one said cartridge, - retention means (42, 47), capable of maintaining the cartridge in a position substantially coaxial to the infusion chamber and the injector device, - an actuation system, capable of causing relative displacements between the injector device and the infusion chamber, between a spaced position and a close position, the infusion chamber being in a fixed position with respect to a stationary structure of the delivery assembly and the injector device being mounted displaceable with respect to the infusion chamber and the said stationary structure, wherein the retention means (42, 47) are capable of assuming a retention position, in which the cartridge is retained in the said position substantially coaxial to the infusion chamber and the injector device, and a release position, in which the cartridge is free to fall towards an outlet passage of the delivery assembly, wherein the retention means comprise - a support element for supporting the cartridge, the support element being sustained in a displaceable way by the injector device in a part thereof that generally faces towards the outlet passage, the support element being switchable from the said retention position to the said release position in the course of the displacement of the injector device towards the said close position; and - guiding means at generally opposite side parts of the injector device, particularly in substantially diametrically opposite positions, the guiding means frontally protruding from the injector device and being capable of laterally constraining the cartridge and guide it to said position substantially coaxial to the infusion chamber, the delivery assembly being characterized in that the guiding means are in a fixed position at said generally opposite side parts of the injector device.