The invention involves a method for processing of machine-readable forms or documents of non-fixed format. The method makes use of, for example, a structural description of characteristics of document elements, a description of a logical structure of the document, and methods of searching for document elements by using the structural description. A structural description of the spatial and parametric characteristics of document elements and the logical connections between elements may include a hierarchical logical structure of the elements, specification of an algorithm of determining the search constraints, specification of characteristics of every searched element, and specification of a set of parameters for a compound element identified on the basis of the aggregate of its components. The method of describing the logical structure of a document and methods of searching for elements of a document may be based on the use of the structural description.