Aspects of the invention relate to techniques of using two-dimensional scan architecture for testing and diagnosis. A two-dimensional scan cell network may be constructed by coupling input for each scan cell to outputs for two or more other scan cells and/or primary inputs through a multiplexer. To test and diagnose the two-dimensional scan cell network, the two-dimensional scan cell network may be loaded with chain patterns and unloaded with corresponding chain test data along two or more sets of scan paths. Based on the chain test data, one or more defective scan cells or defective scan cell candidates may be determined.