Indexing methods for efficient processing of multidimensional data are very requested in many fields, like geographical information systems, drawing documentations etc. Well-known R-tree is one of the multidimensional data structures. The R-tree is based on bounding of spatial near points by multidimensional rectangles. This data structure supports various types of queries, e.g. point and range queries. The range query retrieves all tuples of a multidimensional space in the defined query box. Narrow range query is an important type of the range query including at least one narrow dimension. Despite many variants of R-trees, narrow range query processing is inefficient. In this paper, we depict a modification of Signature R-tree: data structure for the narrow range query processing. This data structure applies signatures for a description of tuples stored in a tree's page. We present an improvement of this technique. Key words: multidimensional data structure, narrow range query, R...