Self-microemulsifying systems (SMES) are among novel approaches for improving oral absorption of drugs with poor biopharmaceutical properties. According to the definition SMES are isotropic mixtures of oils, surfactants, hydrophilic solvents or co-surfactants and drugs that form oil-in-water microemulsions spontaneously following dilution with water or aqueous media upon gentle agitation. The self-emulsification process is specific to the oil/surfactant ratio and surfactant concentration. The main goal of our study was to formulate SMES that are able to form microemulsions with water or aqueous media on wide area of (pseudo)ternary phase diagram. Various combinations of oils (castor oil, linseed oil and PeceolTM), surfactants (Labrasol®, Cremophor® EL and Tween® 20) and co-surfactants (Cremophor® RH 40, Solutol® HS-15 and CapryolTM 90) were studied in order to find optimal oil/surfactant ratio. (Pseudo)ternary phase diagrams were constructed from above mentioned components with titration technique and regions of microemulsions were determined based on organoleptic characteristics/properties and results of specific electrical conductivity. Combination of PeceolTM and castor or linseed oil as oil phase and Cremophor® EL as surfactant was confirmed to form the largest microemulsions area on (pseudo)ternary phase diagram, and the region was even wider after addition of co-surfactants into the system, especially after adding Cremophor® RH 40. Selected S(M)ES that formed the widest microemulsion area on (pseudo)ternary phase diagrams were based on results of droplet size after dilution classified as type III by Pouton; strictly speaking S(M)ES 1-6, 8 and 9 with droplets smaller than 100 nm as type IIIA (SMES) and S(M)ES 7 with droplets smaller than 250 nm as type IIIB (SES). Solubility and stability assessment of model substances NDS 1, NDS 2 and NDS 8 was performed in selected S(M)ES. According to the results S(M)ES 3, 5 and 8 were proven as possible delivery systems for model substance NDS 8, while solubility of model substances NDS 1 and NDS 2 was also very high, but the stability was not adequate.