Fluorescence micro-imaging and homodyne phase-resolved confocal microspectrofluorimetry were used to monitor the transport of antisense oligonucleotide into cancer MCF7 cells and the subsequent intracellular distribution. Phosphorothioate analog of 15-mer oligoadenylate (dA₁₅) labeled by ATTO 425 was complexed with 5,10,15,20-tetrakis (1-methyl-4-pyridyl) porphyrin (H₂TMPyP4) as an uptake-mediating agent. Fluorescence lifetime data within a broad spectral range have revealed properties of both components inside the cell. H₂TMPyP4 lifetime inside the cell is not influenced in this malignant cell line, while the lifetime of modified oligonucleotide was found to be slightly shortened.