Comparative genomic hybridization (CGH) is a molecular cytogentic technique that can characterize excess and missing cytogenetic materiál often unrecognizable by G-banding. Recently, CGH has been further improved as high-resolution CGH which may detect aberrations down to 3-5 Mb and enhance the sensitivity in the detection of aberrations. Although the major application of CGH has been in the field of cancer genetics, the utilization of CGH as a tool in clinical cytogenetics is also increasing. In clinical cytogenetics CGH has been particularly useful by facilitating the identification and characterization of intrachromosomal duplication, deletions, unbalanced translocations and maker chromosomes. We here report the application of the recently developed metod of high resolution CGH (HR-CGH) for clarification of small terminal imbalances in 4 patients with abnormal karyotypes and dysmorphic features. In our work we performed the characterization of de novo alterations such as add(1p), add(4p), add(6p) and add(17p) by using HR-CGH. The results were subsequently confirmed by FISH and spectral karyotyping (SKY).The following findings were der(1)t(1;11), inv(4p), dup(6p) and der(17)t(11;17). We conclude that HR-CGH can be used as excellent diagnostic tool for clarification and identification of chromosomal imbalances not evident on routine cytogenetic analysis.