A medical image diagnosis assisting apparatus, comprising: an abnormal peripheral structure detection means adapted to detect, from a three-dimensional medical image representing a subject's internal structure having a branch structure and a peripheral structure which is a structure located in a periphery of the branch structure and functionally associated with the branch structure, an abnormal peripheral structure which is an abnormal portion of the peripheral structure; a branch structure extraction means adapted to extract the branch structure from the three-dimensional medical image; an association identification means adapted to identify a point in the branch structure functionally associated with each point in the peripheral structure based on position information of each point in the extracted branch structure and to obtain a control area of each branch of the extracted branch structure based on the identified functional correspondence between each point in the peripheral structure and each point in the branch structure; an associated branch structure identification means adapted to identify a portion of the branch structure functionally associated with the abnormal peripheral structure as an associated branch structure (LV R) based on the obtained control area of each branch of the extracted branch structure; and an associated peripheral structure identification means adapted to identify a portion of the peripheral structure functionally associated with the identified associated branch structure as an associated peripheral structure based on the obtained control area of each branch of the extracted branch structure and the identified associated branch structure, wherein the associated peripheral structure is an area functionally associated with the branch structure from the associated branch structure to a periphery leading from the associated branch structure, the apparatus further comprises an abnormal peripheral structure enlargement means adapted to enlarge the abnormal peripheral structure according to a given growth condition representing a degree of future growth of the abnormal peripheral structure; and the associated branch structure identification means is adapted to identify a portion of the branch structure functionally associated with the abnormal peripheral structure after the enlargement as the associated branch structure, wherein said growth condition is defined as an enlargement factor of the abnormal portion of each of a plurality of time points. an abnormal peripheral structure detection means adapted to detect, from a three-dimensional medical image representing a subject's internal structure having a branch structure and a peripheral structure which is a structure located in a periphery of the branch structure and functionally associated with the branch structure, an abnormal peripheral structure which is an abnormal portion of the peripheral structure; a branch structure extraction means adapted to extract the branch structure from the three-dimensional medical image; an association identification means adapted to identify a point in the branch structure functionally associated with each point in the peripheral structure based on position information of each point in the extracted branch structure and to obtain a control area of each branch of the extracted branch structure based on the identified functional correspondence between each point in the peripheral structure and each point in the branch structure; an associated branch structure identification means adapted to identify a portion of the branch structure functionally associated with the abnormal peripheral structure as an associated branch structure (LV R) based on the obtained control area of each branch of the extracted branch structure; and an associated peripheral structure identification means adapted to identify a portion of the peripheral structure functionally associated with the identified associated branch structure as an associated peripheral structure based on the obtained control area of each branch of the extracted branch structure and the identified associated branch structure, wherein the associated peripheral structure is an area functionally associated with the branch structure from the associated branch structure to a periphery leading from the associated branch structure, the apparatus further comprises an abnormal peripheral structure enlargement means adapted to enlarge the abnormal peripheral structure according to a given growth condition representing a degree of future growth of the abnormal peripheral structure; and the associated branch structure identification means is adapted to identify a portion of the branch structure functionally associated with the abnormal peripheral structure after the enlargement as the associated branch structure, wherein said growth condition is defined as an enlargement factor of the abnormal portion of each of a plurality of time points.