The application of natural products for treatment and prevention of various diseases is becoming more important. Not only antibacterial natural preparations are being developed, but also antiviral natural products are investigated. There are two main problems in such investigations: (i) special chemical analysis and data analysis methods have to be used, (ii) not only antiviral effect has to be taken into account, but also cytotoxic and other unwanted effects. In this work, a combination of separation methods (capillary electrophoresis and gas chromatography), spectrophotometric methods, data mining/data analysis methods (hierarchical clusterization, multidimensional scaling and classification and regression tree induction) for clarifying chemical attributes in cytotoxic plant extracts was applied. The selected plants belonged to families: (i) Lamiaceae, (ii) Asteraceae and (iii) Fabaceae. Most cytotoxic were Agastache foeniculum Pursh. Kuntze. and Salvia officinalis L. extracts. Least cytotoxic were Perilla frutescens L. and Satureja Montana L. extracts. The tendency of cytotoxic extracts having abundant concentrations of medium and low electrophoretic mobility cations was clarified.