A system for determining cardiovascular information for a patient, the system comprising: at least one computer system configured to: receive patient-specific data regarding a geometry of at least a portion of an anatomical structure of the patient, the anatomical structure including at least a portion of a plurality of arteries and tissue connected to at least a portion of the plurality of arteries, the tissue and arteries are myocardial tissue and coronary arteries, or brain tissue and intracranial and extracranial arteries; create a three-dimensional model representing the anatomical structure of the patient based on the patient-specific data, said three-dimensional model comprising a three-dimensional geometric model of said at least a portion of a plurality of arteries and a three-dimensional geometric model of the tissue; divide said three-dimensional geometric model of the tissue into tissue volumes; extend the three-dimensional model to form an augmented model by creating additional branches of arteries connected to the downstream end of at least one of the arteries included in the three-dimensional geometric model of said at least a portion of a plurality of arteries, and provided (i) on the epicardial surface or contained within the geometric model of the myocardial wall in the case where the modelled tissue and arteries are myocardial tissue and coronary arteries, or (ii) on the outer layer of brain tissue or contained within the geometric model of the brain tissue in the case where the modelled tissue and arteries are brain tissue and intracranial and extracranial arteries, said extending comprising using morphometric models or physiological branching laws to determine the location and size of said additional branches based on centerlines of the arteries; based on said additional branches, to further subdivide at least one of the tissue volumes into tissue sub-volumes; and determine information regarding blood flow into at least one of the tissue sub-volumes by performing a computational analysis using the extended three-dimensional model and a physiological condition of the patient. receive patient-specific data regarding a geometry of at least a portion of an anatomical structure of the patient, the anatomical structure including at least a portion of a plurality of arteries and tissue connected to at least a portion of the plurality of arteries, the tissue and arteries are myocardial tissue and coronary arteries, or brain tissue and intracranial and extracranial arteries; create a three-dimensional model representing the anatomical structure of the patient based on the patient-specific data, said three-dimensional model comprising a three-dimensional geometric model of said at least a portion of a plurality of arteries and a three-dimensional geometric model of the tissue; divide said three-dimensional geometric model of the tissue into tissue volumes; extend the three-dimensional model to form an augmented model by creating additional branches of arteries connected to the downstream end of at least one of the arteries included in the three-dimensional geometric model of said at least a portion of a plurality of arteries, and provided (i) on the epicardial surface or contained within the geometric model of the myocardial wall in the case where the modelled tissue and arteries are myocardial tissue and coronary arteries, or (ii) on the outer layer of brain tissue or contained within the geometric model of the brain tissue in the case where the modelled tissue and arteries are brain tissue and intracranial and extracranial arteries, said extending comprising using morphometric models or physiological branching laws to determine the location and size of said additional branches based on centerlines of the arteries; based on said additional branches, to further subdivide at least one of the tissue volumes into tissue sub-volumes; and determine information regarding blood flow into at least one of the tissue sub-volumes by performing a computational analysis using the extended three-dimensional model and a physiological condition of the patient.