A machine for the preparation of liquid products via capsules which have a substantially cup-shaped body (6a-6d) that houses a dose of at least one substance that can form a liquid product via a preparation fluid, such as water and/or steam, the machine having a delivery assembly, which comprises a stationary structure and a passage for introduction of capsules, the assembly moreover comprising: - a preparation chamber that includes a first part of chamber, having a housing configured for receiving at least partially a capsule and enabling delivery of the liquid product from the preparation chamber, and a second part of chamber configured for introduction of the fluid into the capsule; - an actuation system controllable for causing displacements of the second part of chamber with respect to the first part of chamber, between a spaced apart position and a close position; - two first guide elements, secured at generally opposite side parts of the second part of chamber and fixed in motion with respect to the second part of chamber, the guide elements being configured for co-operating with a flange of a capsule for guiding the latter towards a position that is substantially coaxial to the first part of chamber and to the second part of chamber, the first guide elements being designed to keep the capsule in a position centred with respect to the first part of chamber in the course of displacement of the second part of chamber towards the close position, at least as far as entry of the capsule into the housing of the first part of chamber; - an ejector member, which is slidably mounted through a through opening of a bottom of the housing of the first part of chamber and is displaceable in the housing between a retracted position and an advanced position, in the course of displacement of the second part of chamber between the spaced apart position and the close position, respectively; and - connection members (8, 9a; 8', 9a; 8", 9a), which connect the ejector member to the second part of chamber, the machine being characterized in that: - the first guide elements are prearranged for interfering with the flange of the capsule in the course of displacement of the second part of chamber from the close position to the spaced apart position in order to extract the capsule from the housing of the first part of chamber; - the connection members (8, 9a; 8', 9a; 8", 9a) are configured in such a way that the ejector member brings about expulsion of the capsule from the housing of the first part of chamber if the first guide elements fail to extract the capsule from the housing. - a preparation chamber that includes a first part of chamber, having a housing configured for receiving at least partially a capsule and enabling delivery of the liquid product from the preparation chamber, and a second part of chamber configured for introduction of the fluid into the capsule; - an actuation system controllable for causing displacements of the second part of chamber with respect to the first part of chamber, between a spaced apart position and a close position; - two first guide elements, secured at generally opposite side parts of the second part of chamber and fixed in motion with respect to the second part of chamber, the guide elements being configured for co-operating with a flange of a capsule for guiding the latter towards a position that is substantially coaxial to the first part of chamber and to the second part of chamber, the first guide elements being designed to keep the capsule in a position centred with respect to the first part of chamber in the course of displacement of the second part of chamber towards the close position, at least as far as entry of the capsule into the housing of the first part of chamber; - an ejector member, which is slidably mounted through a through opening of a bottom of the housing of the first part of chamber and is displaceable in the housing between a retracted position and an advanced position, in the course of displacement of the second part of chamber between the spaced apart position and the close position, respectively; and - connection members (8, 9a; 8', 9a; 8", 9a), which connect the ejector member to the second part of chamber, - the first guide elements are prearranged for interfering with the flange of the capsule in the course of displacement of the second part of chamber from the close position to the spaced apart position in order to extract the capsule from the housing of the first part of chamber; - the connection members (8, 9a; 8', 9a; 8", 9a) are configured in such a way that the ejector member brings about expulsion of the capsule from the housing of the first part of chamber if the first guide elements fail to extract the capsule from the housing.