Problems and procedure of the lithium abundance determination in the atmospheres of superlithium C giants using the resonance Li I line λ 670.8 nm and subordinate lines λλ 812.6, 610.4, and 497.2 nm are considered. LTE and NLTE lithium abundances from these lines in the atmospheres of J stars WZ Cas (logN(Li) = 4.7, 4.9) and WX Cyg (4.6, 4.8) were determined. We found that among the subordinate Li I lines the line λ 497.2 nm is the best lithium abundance indicator in the spectra of superlithium C giants.